Premature chromosome condensation

Bleomycin induced chromosomal damage in Chinese hamster bone marrow gives rise to micronuclei by means of lagging chromatin main and micronuclei eventually become asynchronous in consecutive cell cycles and mitosing main nuclei induce premature chromosome condensation in the micronuclei (Kurten and Obe, 1975). 

Kurten S, Obe, G (1975) Premature chromosome condensation in the bone marrow of Chinese hamster after pUcation of bleomycin in vivo. Mutat Res 27(2) 285—294 Lee DY, Hayes JJ, Pruss D, Wolffe AP (1993) A positive role for histone acetylation in transcription factor access to nucleosomal DNA. Cell 72 73—84... 

Dresp J, Bauchinger M. 1988. Direct analysis of the clastogenic effect of formaldehyde in unstimulated human lymphocytes by means of the premature chromosome condensation technique. 

These differences in transcriptional activity between the male and female pronuclei likely reflect the different origins of the male and female pronuclei that may lead to intrinsic underlying differences in nuclear/chromatin structure. Such differences may account for the observation that fusion of zygotic halves containing either a female or male pronucleus with a metaphase Il-arrested egg resulted in a more rapid premature chromosome condensation of the maternal chromatin, which also achieved a greater degree of condensation than its paternal counterpart (Ciemerych and Czolowska, 1993). 

These toxins can influence the cell cycle by a complex series of direct and indirect actions on a variety of molecular targets by inhibiting protein phosphatases, hence altering the phosphorylation state of proteins involved in the control of the cell cycle. Exposine of mammalian cells to OA leads to hyperphosphorylation and activation of cyclin-dependent kinase 1-cyclin B complex (CDKl-cyc-lin B, called also M-phase-promoting factor, MPF or Cdc2-cyclin B), which leads the cells to G2/M transition and to a mitosis-like state, characterized by a premature chromosome condensation and break of the nuclear lamina. This event seems to depend mainly on the inhibition of protein phosphatase 2A, which is necessary to maintain the complex CDKl-cydin B in its inactive form. Nevertheless, inhibition of other phosphatases, such as protein phosphatases 4 and 5, could mediate. 

Pantelias GE, Maillie HD (1983) A simple method for premature chromosome condensation induction in primary human and rodent cells using polyethylene glycol. Som Cell Genet 9 533-547... 

ESR, electron-spin resonance PCC premature chromosome condensation. 

At the end of the S period, the cell enters in the G2 period. It is believed that condensation of chromosomes occurs as a result of synthesis of a number of uncharacterized factors as the cell enters the D phase from the G2 phase. This is the beginning of the prophase of mitosis. The HeLa cell in mitosis can cause premature chromosome condensation (chromosomal pulverization) of an interphase nucleus that enters the cell by cell fusion (Johnson and Rao, 1970 Matsui et al., 1972). The chromosomal condensation factor is not species specific (Johnson et al., 1970). Arrest of the G2 phase may occur but usually involves only a few percent of the cells. It has been studied best in the mouse ear epidermis (Gelfant, 1963). Cyclic AMP may mediate the reversible arrest of cells in the G2 phase (Nose and Katsuta, 1975 Willingham et al., 1972). Fusion of a HeLa cell in the G2 phase with a cell in an earlier phase can arrest the G2 phase and prevent progression into the D phase (Rao et al., 1975 Rao and Johnson, 1970). Protein synthesis is necessary until 10 min before prophase in order for cells to enter into mitosis (Tobey et al., 1966). RNA synthesis is also required but is completed before the protein synthesis requirement (Tobey et al., 1966). 

Johnson, R. T., and Rao, P. N., 1970, Mammalian cell fusion Induction of premature chromosome condensation in interphase nuclei. Nature 226 717. 

El Achkar E, Gerbault-Seureau M, Muleris M, Dutrillaux B, Debatisse M. Premature condensation induces breaks at the interface of early and late replicating chromosome bands bearing common fragile sites. Proc. Natl. Acad. Sci. U.S.A. 2005 102 18069-18074. 

Catastrophic genetic damage can occur If cells progress to the next phase of the cell cycle before the previous phase is properly completed. For example, when S-phase cells are induced to enter mitosis by fusion to a cell In mitosis, the MPF present In the mitotic cell forces the chromosomes of the S-phase cell to condense. However, since the replicating chromosomes are fragmented by the condensation process, such premature entry into mitosis is disastrous for a cell. 

Scoring for aberrations in substituted G2 cells with premature condensed chromosomes reveals that the appearance of G2 delay induced by the CldUrd coincides with an enhanced number of aberrations. Treatment with 1 mM SAB increases this frequency and with 10 n M SAB, similar to metaphase cells, no significant increase can be observed. 

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