Sequential steps in DNA replication are inhibited to ensure reduction of ploidy in meiosis.

Meiosis involves two successive rounds of chromosome segregation without an intervening S phase. Exit from meiosis I is distinct from mitotic exit, in that replication origins are not licensed by Mcm2-7 chromatin binding, but spindle disassembly occurs during a transient interphase-like state before meiosis II. The absence of licensing is assumed to explain the block to DNA replication, but this has not been formally tested.

Selective inhibition of histone deacetylase 6 (HDAC6) induces DNA damage and sensitizes transformed cells to anticancer agents.

Histone deacetylase 6 (HDAC6) is structurally and functionally unique among the 11 human zinc-dependent histone deacetylases. Here we show that chemical inhibition with the HDAC6-selective inhibitor tubacin significantly enhances cell death induced by the topoisomerase II inhibitors etoposide and doxorubicin and the pan-HDAC inhibitor SAHA (vorinostat) in transformed cells (LNCaP, MCF-7), an effect not observed in normal cells (human foreskin fibroblast cells). The inactive analogue of tubacin, nil-tubacin, does not sensitize transformed cells to these anticancer agents.

Analysis of Mcm2-7 chromatin binding during anaphase and in the transition to quiescence in fission yeast.

Mcm2-7 proteins are generally considered to function as a heterohexameric complex, providing helicase activity for the elongation step of DNA replication. These proteins are loaded onto replication origins in M-G1 phase in a process termed licensing or pre-replicative complex formation. It is likely that Mcm2-7 proteins are loaded onto chromatin simultaneously as a pre-formed hexamer although some studies suggest that subcomplexes are recruited sequentially.

In situ assay for analyzing the chromatin binding of proteins in fission yeast.

An in situ technique for studying the chromatin binding of proteins in single fission yeast cells (Schizosaccharomyces pombe) is described. Cells are permeabilized by enzymatic digestion and extracted with a detergent-containing buffer. This procedure removes soluble proteins, but proteins that are bound to insoluble cell structures such as chromatin are retained, and overall cell morphology is maintained.

The regulation of competence to replicate in meiosis by Cdc6 is conserved during evolution.

DNA replication licensing is an important step in the cell cycle at which cells become competent for DNA replication. When the cell cycle is arrested for long periods of time, this competence is lost. This is the case for somatic cells arrested in G0 or vertebrate oocytes arrested in G2.

Fission yeast Cdc23/Mcm10 functions after pre-replicative complex formation to promote Cdc45 chromatin binding.

Using a cytological assay to monitor the successive chromatin association of replication proteins leading to replication initiation, we have investigated the function of fission yeast Cdc23/Mcm10 in DNA replication. Inactivation of Cdc23 before replication initiation using tight degron mutations has no effect on Mcm2 chromatin association, and thus pre-replicative complex (pre-RC) formation, although Cdc45 chromatin binding is blocked. Inactivating Cdc23 during an S phase block after Cdc45 has bound causes a small reduction in Cdc45 chromatin binding, and replication does not terminate in the absence of Mcm10 function.