MAE 545: Lecture 9 (10/15) Cell division in higher organisms. Cell division in bacteria

Transcription

1 MAE 545: Lecture 9 (10/15) Cell division in higher organisms Cell division in bacteria

2 PANEL 17 1: Principle Stages M Phase (Mitosis Cytokinesis) in an Animal Cell 980 M Phase (Mitosis(Mitosis Cytokinesis) in an Animal Cell 17 1: Stages MCytokinesis) Phase (Mitosis Cytokinesis) in an Animal Cell Stages MPrinciple Phase in an Animal Cell PANEL 17 1: Principle Stages M Phase (Mitosis 980 NEL 17 1: Principle Stages M Phase (Mitosis Cytokinesis) in an Cytokinesis) Animal Cell in an Animal Cell ase (Mitosis PANEL Cytokinesis) anprinciple Animal Cell 17 1: in Stages 980(Mitosis f M Phase Cytokinesis) in an Animal Cell M Phase (Mitosis Cytokinesis) in an Animal Cell eciple Stages M Phase (Mitosis Cytokinesis) in an Animal Cell Stages M Phase (Mitosis Cytokinesis) in Animal Cell EL 17 1: Principle Stages M Phase (Mitosisan Cytokinesis) in an Animal Cell 1 PROPHASE At prophase, ASE At prophase, 4 ANAPHASE At prophase, 4 ANAPHASE, daughter At prophase, At anaphase,, PHASE 1 PROPHASE, daughter At prophase, At prophase, closely At anaphase,, intact chromatids synchronously closely forming closely, ing, 4 ANAPHASE associated chromatids, chromatids synchronously forming 1 PROPHASE closely ophase, 4 ANAPHASE separate to form prophase, associated chromatids, At prophase, forming associated chromatids, tic At 4 4ANAPHASE daughter ANAPHASE closely At prophase, Outside closely daughter At anaphase At prophase, osomeintact condense. HASE separate to form, associated chromatids, me mosomes, forming At anaphase, daughter,, condense. Outside dle At prophase,forming daughter Cell division in higher organisms Prophase, condense. Outside associated chromatids,, associated chromatids, nucleus, condense. Outside sting closely, closely nucleus,, nucleus, closely closely condense. Outside condense. Outside intact closely assembles forming nucleus, iated chromatids, forming assembles chromatids, associated chromatids, forming closely assembles associated chromatids, associated nucleus, forming associated chromatids, nucleus, s, have ense. Outsideassembles s, have condense. Outside associated chromatids, have condense. Outside s, condense. Outside assembles condense. Outside assembles apart. moved s, have eus, nucleus, moved apart. condense. Outside apart. nucleus, moved nucleus, s, have nucleus, s, have For simplicity, only three moved apart. mbles assembles For simplicity, only three assembles nucleus, For simplicity, onlymoved three apart. assembles assembles moved apart. shown. In Forhave simplicity, threehave osomes, shown. In s, haveonly assembles s, only shown. In s, have For simplicity, three s, have For simplicity, only three diploid cells, re would be shown. In cated moved diploid cells, re would be apart. moved apart. moveddiploid apart. s, have cells, re would bein shown. moved moved apart. shown. In apart. copies chromodiploid cells, re would be copies chromoimplicity, only three For simplicity, only three For simplicity, only three moved apart. diploid copiescells, chromore would be For simplicity, only three For simplicity, only three diploid cells, re would be some present. In some present. Inshown. shown. In In copies chromomosomes shown. In For simplicity, only some present. In three copies chromo shown. In shown. In condensing chromosome, copies chromluorescence micrograph, diploid cells, re would be fluorescence micrograph, diploid cells, re would be some present. In id cells, re would be shown. In cated chromosome, fluorescence micrograph, some ir present. In chromatids held toger along length diploid cells, re would be re would be copies chromosome present.cells, In g stained stained chromoatids held toger along ir length micrograph, copies copies fluorescence chromodiploid cells, re would bediploid chromosome, stained fluorescence micrograph, copies chromoir length condensing chromosome, copies chromosome present. In fluorescence micrograph, orange some present. In orange held toger along ir length stained eromatids present. In copies length chromostained chromatids held toger along ir onsisting some present. Inmicrograph, orange fluorescence some present. In stained green. fluorescence micrograph, green. orange some present. In escence micrograph, ong ir length fluorescence micrograph, orange green. ing stained condensing chromosome, fluorescence micrograph, plicated chromosome, orange stained fluorescence micrograph, green. mosomes stained ir length green. chromatids held toger along ir length orange stained matids held toger along ir length stained orange green. stained ge green. orange orange orange n. green. green. green. green. mosome in active motion chromosome in active motion chromosome in active motion chromosome in active motion microtubule chromosome in active motion chromosome in active motion chromosome in active motion some in active motion microtubule ctive motion chromosome in active motion chromosome in active motion microtubule shortening microtubule shortening microtubule shorteningshortening shortening shortening microtubule microtubule microtubule microtubule 5 pole pole pole moving outwardpole moving outward moving outward moving outward TELOPHASE During telophase, 5 TELOPHASE sets daughter chromoduring telophase, set daughter 5 TELOPHASE somes arrive at poles 5TELOPHASE TELOPHASE During telophase, chromosets daughter at pole decondense. During telophase, 5 TELOPHASEset daughter sets daughter chromoduring telophase, somes arrive at poles interpolar interpolar interpolar interpolar interpolar interpolar 6 6 set, begins completing formation end completing formation with contraction mitosis. endset, mitosis. nuclei marking nuclei marking division cytoplasm nuclei marking division cytoplasm end ring. mitosis. end mitosis. begins contraction begins with contraction end with mitosis. division cytoplasm division cytoplasm ring. ring. division cytoplasm begins with contraction begins with contraction contraction begins ring. with reassembling ring. around individual ring. reassembling reassembling around individual around individual reassembling reassembling around individual reassembling around individual around individual Cytokinesis CYTOKINESIS During cytokinesis, 6 CYTOKINESIS 6 CYTOKINESIS cytoplasm divided in Duringiscytokinesis, completed by a ring cytokinesis, 6 CYTOKINESIS During cytoplasm is divided in surrounds decondensing completed CYTOKINESIS 6 CYTOKINESIS actinby myosin cytokinesis, a ring is divided in cytoplasm surrounds decondensing During completed filaments, pinches During actin is myosin During cytokinesis, cytoplasm divided in by acytokinesis, ring surrounds completed decondensing cell individed to create filaments, pinches cytoplasm is divided cytoplasm is in by a ring actin myosinin surrounds decondensing completed completed daughters, cell in create by afilaments, ring actin myosin by a ring to with pinches surrounds decondensing surrounds decondensing daughters, one actin myosin filaments, pinches nucleus. myosin actin cell inwith to create e at, midway equator at equator At, At metaphase, at equator aligned at equator atmetaphase e one filaments, pinches cell in nucleus. to create filaments, pinches daughters, with create cell in to create with cell daughters, in to one nucleus. with nucleus. one daughters, daughters, with one nucleus. one nucleus. ring creating cleavage ring furrow creating cleavage furrow ring ring creating cleavage creating cleavage furrow ring ring furrow creating cleavage creating cleavage furrow furrow Alberts et al., Molecular Biology Cell microtubule chromatids issynchronously pulled slowly chromatids synchronously chromatids synchronously separate to form toward itis pulled slowly separate to form pole separate to form separate to form pole it toward daughter, faces.daughter, daughter, daughter, faces. is pulled get shorter, is pulled slowly isslowly pulled slowly isalso pulled slowly shorter, toward pole it poles toward pole it itget toward pole toward pole italso poles faces. move apart; both faces. faces. faces. move apart; both get shorter, processes contribute get shorter, get to shorter, get processes chromosome segregation. poles also poles also contribute poles also shorter,to chromosome poles also segregation. move apart; both move apart; both move apart; both pole move apart; both processes contribute processes contribute processes contribute to to to moving outward poleprocesses contribute to chromosome segregation. chromosome segregation. chromosome segregation. moving outward chromosome segregation. During telophase, set daughter at ring pole sets A new somes daughter chromoarrive at poles decondense. starting to sets daughter chromo set daughter at pole sets daughter reassembles around chromoset daughter somes arrive at poles ring contract decondense. set daughter somes arrive at somes Apoles new at pole starting ring at poles set, completing arrive formation at pole decondense. Ato new at pole decondense. reassembles around starting to contract ring decondense. nuclei marking A new reassembles around ring startingcontract to A new ring set, completing formation A new to end mitosis. starting to reassembles around formation set, completing contract starting reassembles around nuclei marking contract reassembles around division cytoplasm nuclei marking set, completing formation contract Metaphase poles. midway,, midway metaphase, aligned etaphase, atat aligned, midway equator At, metaphase, at midway poles. poles. aligned at equator at equator mosomes aligned poles., midway aligned pole poles. midway chromatids to At midway metaphase, at equator, e equator at equator, poles. chromatids to chromatids opposite poles aligned to to, midway poles. poles. le, midway, midway chromatids to chromatids opposite poles opposite poles. at equator poles. pindle poles. chromatids to poles poles. opposite poles opposite.., midway chromatids chromatids to ochore. opposite polesto. chromatids to opposite poles to poles. chromatids to poles opposite h chromatids. microtubule opposite poles opposite poles. site. poles.. chromatids to le. microtubule opposite poles. 9 Telophase 5 chromosome in active motion HASE 3 METAPHASE APHASE 3 METAPHASE at at me atat metaphase, pole PHASE pole aligned, At metaphase, At metaphase At metaphase, At metaphase, at at equator aligned aligned aligned At metaphase, 3 METAPHASE pole aligned 981 daughter At anaphase, At anaphase,, daughter chromatids synchronously Prometaphase Prometaphase starts Prometaphase starts abruptly with Prometaphase starts abruptlyfragments with Prometaphase fragments starts Prometaphase starts ope breakdown abruptly with abruptly with breakdown breakdown ments at. Chromosomes Prometaphase starts ETAPHASE abruptly with abruptlyfragments with. Chromosomes etaphase starts breakdown 2 PROMETAPHASE breakdown. Chromosomes earfragments fragments starts Prometaphase starts can pole now to abruptly Prometaphase breakdown breakdown can now to ptly with with Chromosomes. Chromosomes Prometaphase starts can. now to abruptly withchromosomes via ir breakdown abruptly with. at. Chromosomes agments can pe via ir can now to kdown now to abruptly with via ir fragments breakdown s now undergo pole Chromosomes. fragments can can to breakdown uclear now to ir s undergo lope. Chromosomes via ir s via undergo. Chromosomes breakdown active can nowmovement. to via ir. Chromosomes via ir s undergo active movement. now toat s to undergo active movement.. Chromosomes can now via ir s undergo can nowmovement. to pole active s undergo otubules via ir active movement. can now to via ir via ir active movement. s undergo active movement. via ir ochores undergo s undergo active movement. s undergo e movement. active movement. s undergo active movement. active movement Anaphase g 2 PROMETAPHASE TAPHASE Prometaphase starts METAPHASE abruptly with 2 PROMETAPHASE Prometaphase starts re-formation interphase interphase array re-formation nucleated array nucleated by by re-formation interphase re-formation interphase (Micrographs courtesy Julie Canman Ted Salmon.) array nucleated (Micrographs courtesy Julie Canman Ted Salmon.) array nucleated re-formation interphase by re-formation interphase by arraynucleated nucleated array by (Micrographs courtesy Julie Canman Ted Sa

3 Cell division 3

4 Growing can push s to middle cell (A) (B) tubulin subunits growing force due to pushing on wall minutes 3 6 Figure 16.51: Sel s. (A) D time sequence a experiment. Initial added to a micra well along with so subunits. As ce growth microtub grow process dynami microtubule tip co chamber, it can resulting in a push. Event grow against wall in finds a geometrical ce Frames from a vide differential interfer microscopy show t period several m from T. E. Holy et a Sci. USA 94:6228, 10 mm R. Phillips et al., Physical Biology Cell this phenomenon is exploited by4 cells to set up a universal coor-

5 Spindle is organized by molecular motors kinesin-14 + dynein microtubule kinesin dynein + plasma membrane kinesin-4,10 chromatids + (metaphase) 5 Alberts et al., Molecular Biology Cell

6 Biology Vol 15 No 23 Microtubules depolymerized at poles ding ding F sliding + V depoly (A) V depoly Pole Pole speckles Depolymerization is done by molecular motors D.J. Odde, Current Biol. 15, R956-R959 (2005) Current Biology Figure 2. A hypotical model for force-assembly coupling at pole. (A) Microtubule minus ends embedded in pole (dark blue) tend to depolymerize slowly when under low sliding force (F sliding ). That depolymerization occurs at all may be because a depolymerase (red circles), such as Klp10A (Kinesin- 13), acts at pole to Pole increase depolymerization velocity (V depoly ) locally. (B) If sliding force is increased, n concentration depolymerase 6 increases locally so that pole TUBULIN REMOVAL below a threshold concentration Kinesin-5. Goshima et al. [2] acknowledge that or coupling assumptions might be considered as well, that furr evaluation will be needed. For example, recent analysis budding yeast Xenopus extract s suggest that tension on can trigger a bias towards assembly, or attenuation disassembly, at plus ends [10,11]. Neverless, model makes a surprising prediction about stability that turns TUBULIN ADDITION TUBULIN ADDITION speckles moving poleward TUBULIN REMOVAL out to be true. Alberts et al., Molecular Biology Cell

7 Microtubules to via centromere region chromosome chromosome plus end microtubule (B) chromatid depolymerization (C) at poles produces tension Ndc80 complex (A) UNSTABLE Tension sensed by s increases binding affinity for locks m in correct ment (B) UNSTABLE (C) UNSTABLE 7 (D) STABLE Alberts et al., Molecular Biology Cell

8 Cell division Once all correctly ed to, y break into pair chromatids, n pulled towards s Contractile ring involving actin myosin motors divides cell in 8 Alberts et al., Molecular Biology Cell

9 Spindle length is similar across cells Spindles in Drosophila cells 10µm cell nuclei poles G. Goshima et al., Current Biol. 15, (2005) 9

10 How various factors affect length? Certain factors removed with RNA interference G. Goshima et al., Current Biol. 15, (2005) 10

11 Model for length control 11 G. Goshima et al., Current Biol. 15, (2005)

12 Sliding force pushes s apart G. Goshima et al., Current Biol. 15, (2005)! F sliding = L 1 v sliding v (max) sliding proportional to density sliding motors a Velocity (nm s 1 ), 5 µm ATP b mm ATP 5 µm ATP Load (pn) Velocity (nm s 1 ), 2 mm ATP 12 K. Visscher et al., Nature 400, (1999)

13 Kinetochore pulls inwards F kt = F kt,0 constant tension force s 13 G. Goshima et al., Current Biol. 15, (2005)

14 Restoring spring forces try to keep at rest length S0 S 0 F tension = (S S 0 ) 14 G. Goshima et al., Current Biol. 15, (2005)

15 Model for length control F sliding = L 1 F kt = F kt,0 F tension = (S S 0 ) ds dt = 2(F sliding F kt F tension ) µ assuming viscous drag G. Goshima et al., Current Biol. 15, (2005) v sliding v (max) sliding! 15 dl dt =2(v poly v sliding ) ds dt =2(v sliding v depoly ) dl dt + ds dt =2(v poly v depoly ) No steady state if rates microtubule polymerization depolymerization different!

16 Depolymerization rate depends on sliding force A V depoly F sliding B + F sliding V depoly Pole Pole + v depoly = v 0 dep + v (max) dep Current Biology 1 e F sliding/ D.J. Odde, Current Biol. 15, R956-R959 (2005) 16 G. Goshima et al., Current Biol. 15, (2005)

17 Model for length control S = S 0 F kt + ln ln L = 1 v (max) v (max) dep dep +v 0 dep v poly v poly v (max) sliding v (max) dep v (max) dep + v 0 dep v poly! L<S under normal conditions in experiments. Is re a new phase when L>S? proportional to density sliding motors global spring constant tension s s 17 G. Goshima et al., Current Biol. 15, (2005)

18 Spindle bistability no normal concentration sliding motors 18 G. Goshima et al., Current Biol. 15, (2005)

19 Cell division in bacteria 19

20 Genetic information in bacteria One large circular DNA A few small circular plasmids Plasmids carry additional genes that have recently evolved may benefit survival (e.g. antibiotic resistance) 20

21 VES Spontaneous demixing due to steric excluded volume interactions b a Genome-sized dsdna Blob Supercoiled plectonemes Topologically independent structural unit Blobs newly synsized DNA Stretching twisting Stabilization by nucleoidassociated proteins Nucleoidassociated protein Close packing string blobs Simultaneous replication demixing chromosome teins such as (ParM) ctive transport ds ori loci, sisting ParA, ite for ParB) is cteria conc. crescentus olerae. plays an imporregation, its role following reanot required beginning e ParA alone me segregation ParA homoscuss below, demix heir separation e pushing or A28. A potential t chromohat undergo DNA replication segregation Molecular crowding nucleoid compaction create a concentric shell in nucleoid periphery S. Jun A. Wright, Nat. Rev. Wikipedia Figure 2 Physical model a bacterial chromosome its segregation. a A8,reductionist model Microbiology (2010) Naturenaked Reviews Microbiology Escherichia coli chromosome. First, we stretch a bacterial-genome-sized double-stred 21 DNA (dsdna). This breaks DNA into a series blobs, total volume gradually decreases

22 Topoisomerase 1 2 release tension along DNA speed up separation process Separation by reptation is slow Separation by type II topoisomerase can be fast despite occasional reverse str-passing S. Jun A. Wright, Nat. Rev. Microbiology 8, (2010) 22

23 Bacteria divide faster than DNA replicates Under normal conditions E. coli divides every min In E. coli it takes ~40 min to replicate DNA How can bacteria divide faster than DNA replicates? Multiple replication forks! Bacteria starts replicating DNA for ir daughters, gr daughters, etc. 23

24 Plasmid segregation Plasmids too small to spontaneously segregate on different sides bacteria plasmid ParM ParM plasmid monomers (A) origin replication ParM filaments ParM is analogous to actin (assembly by ATP hydrolysis) ParR proteins (B) 2 µm Alberts et al., Molecular Biology Cell 24

25 Contraction FtsZ-ring divides bacterial cell in FtsZ is analogous to tubulin (assembly by GTP hydrolysis) Bacterial division is extremely precise. FtsZ forms at (0.50 ± 0.01) L (A) 1 µm How does bacteria know where to place ring? 25

26 Min system oscillations provide cues for formation FtsZ ring FtsZ MinC MinD MinE Predator-prey like dynamics MinD MinE proteins produce oscillations on a minute time scale, is much shorter than typical division time (~20 min). On average MinC/MinD proteins depleted near cell center, where FtsZ ring forms! 0s time <ρ(x)>/ρ max MinD x (µm) MinE x (µm) s H. Meinhardt P.A.J. de Boer, PNAS 98, (2001)

27 Min system oscillations in large cells MinD oscillations in normal E. Coli MinD oscillations in E. Coli, where division is prevented (A) (B) 0 s 20 s 40 s 60 s 1 mm 0 s 20 s 40 s 5 mm R. Phillips et al., Physical Biology Cell 27