Sister cohesion

Nasmyth Do you even need terms like GT or GO These are purely phenomenological terms. One thesis is that we just talk about real things, as opposed to phenomenological things. Do you mean by G2 that the cell is a 4C cell In which case, why not just say that it is a 4C cell. Does it have sister chromatid cohesion or not Is Cdkl in some form or another active or non-active Most of these terms are hangovers from a past when we didn t know anything about the mechanism of the cell cycle. We should just stop using them. 

Abstract. In eukaryotic cells, replicated DNA molecules remain physically connected from their synthesis in S phase until they are separated during anaphase. This phenomenon, called sister chromatid cohesion, is essential for the temporal separation of DNA replication and mitosis and for the equal separation of the duplicated genome. Recent work has identified a number of chromosomal proteins required for cohesion. In this review we discuss how these proteins may connect sister chromatids and how they are removed from chromosomes to allow sister chromatid separation at the onset of anaphase. 

Loss of sister chromatid cohesion would therefore be sufficient for the sudden movement of chromatids to opposite poles at the metaphase to anaphase transition. According to this hypothesis, a specific apparatus binds chromatids together during replication, holds them in an orientation that facilitates the attachment of sister kinetochores to spindles extending to opposite poles, and resists the splitting force that results from this bipolar attachment to the spindle. Destruction of this specialized cohesive structure triggers movement of chromatids to opposite poles at the onset of anaphase. 

Despite these valuable insights, over a century of cytological observation has shed little light on the identity of the sister chromatid cohesion apparatus. In the absence of a biochemical approach, one way forward was inspired guesswork. Once it appeared likely that chromosomes contained one double stranded DNA... 

FIG. 6. (A) A two step model for the sequential loss of sister chromatid cohesion in animal... 

The pall of fog that has shrouded the sister separation process for over a century is starting to lift and this long mysterious process has started to reveal its secrets. There is now convincing evidence that the sudden movement of chromosomes to the poles at the onset of anaphase is triggered by cleavage of specific sister chromatid cohesion proteins. Future research must address the structural basis of cohesion and how it is established only at replication forks. It must also address the generality of mechanisms that dismantle cohesion at the metaphase to anaphase transition and how mistakes in this process contribute to human disease. 

Ciosk R, Zachariae W, Michaelis C, Shevchenko A, Mann M, Nasmyth K 1998 An ESP1 /PDS1 complex regulates loss of sister chromatid cohesion at the metaphase to anaphase transition in... 

Furuya K, Takahashi K, Yanagida M 1998 Faithful anaphase is ensured by Mis4, a sister chromatid cohesion molecule required in S phase and not destroyed in G1 phase. Genes Dev 12 3408-3418... 

Guacci V, Koshland D, Strunnikov A 1997 A direct link between sister chromatid cohesion and chromosome condensation revealed through the analysis of MCD1 in S. cerevisiae. Cell... 

Kerrebrock AW, Moore DP, Wu JS, Orr-Weaver TL 1995 Mei-S332, a Drosophila protein required for sister-chromatid cohesion, can localize to meiotic centromere regions. Cell 83 247-256... 

Klein F, Mahr P, Galova M et al 1999 A central role for cohesins in sister chromatid cohesion, formation of axial elements, and recombination during yeast meiosis. Cell 98 91-103... 

Losada A, Hirano M, Hirano T 1998 Identification of Xenopus SMC protein complexes required for sister chromatid cohesion. Genes Dev 12 1986-1997 Maguire MP 1990 Sister chromatid cohesiveness vital function, obscure mechanism. Biochem Cell Biol 68 1231-1242... 

Miyazaki WY, Orr-Weaver TL 1994 Sister chromatid cohesion in mitosis and meiosis. Annu Rev Genet 28 167-187... 

Sigrist S, Jacobs H, Stratmann R, Lehner CF 1995 Exit from mitosis is regulated by Drosophila fizzy and the sequential destruction of cyclins A, B and B3. EMBO J 14 4827-4838 Skibbens RV, Corson LB, Koshland D, Hieter P 1999 Ctf7p is essential for sister chromatid cohesion and links mitotic chromosome structure to the DNA replication machinery. Genes... 

Phosphorylation has been thought to be correlated to the mitotic chromatin condensation and the transcriptional regulation in interphase (Nowak and Corces, 2004). The mitotic phosphorylation, which was first identified in 1978 (Gurley et al, 1978), occurs at Ser (Wei et al, 1998), Ser (Goto et al, 1999), and Thr (Preuss et al, 2003) in histone H3. The Ser phosphorylation is catalyzed by the aurora kinase family (de la Barre et al, 2000), and is required for the initiation of chromosome condensation but not for its maintenance (dephosphorylation of mitotic chromosomes does not induce chromosome decondensation) (Van Hooser et fl/.,1998). In meiosis, Ser phosphorylation is also required for the cohesion of sister chromatids rather than the condensation (Kaszas and Cande, 2000). 

Karymov MA, Tomschik M, Leuba SH, Caiafa P, Zlatanova J (2001) DNA methylation-dependent chromatin fiber compaction in vivo and in vitro requirement for hnker histone. Faseb J 15 2631—2641 Kaszas E, Cande WZ (2000) Phosphorylation of histone H3 is correlated with changes in the maintenance of sister chromatid cohesion during meiosis in maize, rather than the condensation of the chromatin. J Cell Sci 113(Pt 18) 3217-3226... 

Anaphase. After the spindle has been checked, a sudden loss of cohesion between the sister chromatid pairs allows them to move toward the opposite poles. This process is catalyzed by the anaphase-promoting complex (APC, or cyclosome) and its activator protein Cdc20, a large multiprotein complex.225 The APC also promotes proteolytic breakdown of cyclins and other... 

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