No abstract

Oxam¯atin [(2E) -5 -[3 -[(phenylsufonyl) amino] phenyl]-pent-2-en-4-ynohydroxamic acid] induces transcriptional activation of junD and morphological reversion in various NIH3T3-derived transformed cell lines. We found that oxam¯atin showed in vitro antiproliferative activity against various mouse and human tumor cell lines with drastic changes in the cell morphology and in vivo antitumor activity against B16 melanoma. Oxam¯atin caused an elongated cell shape with ®lamentous protrusions as well as arrest of the cell cycle at the G1 phase in HeLa cells. These phenotypic changes of HeLa cells were apparently similar to those by trichostatin A (TSA), a speci®c inhibitor of histone deacetylase (HDAC). The e ect of oxam¯atin on the transcriptional activity of the cytomegalovirus (CMV) promoter was examined and compared with known HDAC inhibitors, TSA, sodium n-butyrate, and FR901228. Oxam¯atin as well as all these inhibitors greatly enhanced the transcriptional activity of the CMV promoter in a dose-dependent manner. Oxam¯atin, like TSA, inhibited intracellular HDAC activity, as a result of which marked amounts of acetylated histone species accumulated. Finally, e ects on expression of several endogenous genes involved in cell morphology and cell cycle control in HeLa cells were analysed. Expression of gelsolin, cyclin E and Cdk inhibitors including p21 WAF1/Cip1 was highly augmented, while that of cyclin A and cyclin D1 was decreased by oxam¯atin. These results suggest that changes in the expression pattern of the genes regulating cell morphology and the cell cycle due to histone hyperacetylation are responsible for the antitumor activity, the morphological change and the cell cycle arrest induced by oxam¯atin.

Inhibitors of histone deacetylase (HDAC) block cell cycle progression at Gl in many cell types. Weinvestigated the mechanism by which trichostatin A (TSA), a specific inhibitor of HDAC, induces Gl arrest in human cervix carcinoma HeLa cells. TSAtreatment induced histone hyperacetylation followed by growth arrest in Gl as well as hypophosphorylation of pRb. The Cdk4 kinase activity was essentially unchanged during the TSA-induced Gl arrest. On the other hand, the arrest was accompanied by down-regulation of kinase activity of Cdk2, although the total protein levels of Cdk2 and its activator Cdc25A were unaffected. Upon TSA treatment, amounts of cyclin E and the CDKinhibitor p2lWAF1/QP1were markedly increased, while that of cyclin A was reduced. The induction of p21 and down-regulation of cyclin A correlated well with the decreased Cdk2 activity and cell cycle arrest. Furthermore, gel filtration chromatography showed the association of p21 with the cyclin E-Cdk2 complex, suggesting that the activation of Cdk2 by the enhanced expression of cyclin E is blocked by the increased p21. The elevated expression of p21 is also observed in cells treated with trapoxin and FR901228, structurally unrelated histone deacetylase inhibitors.A human colorectal carcinoma cell line lacking both alleles ofthep21 gene (p21 -/-) was resistant to TSAseveral times more than the parental line (p21 +/+). These results suggest that the suppression of Cdk2 kinase activity due to p21 overexpression play a critical role in HDACinhibitor-induced growth inhibition.

No abstract

A gene named phd1 + encoding a protein highly homologous to the yeast and human histone deacetylases, such as Saccharomyces cerevisiae Rpd3p and human HDAC1, was cloned from Schizosaccharomyces pombe. The immune complex isolated from S. pombe cells expressing Phd1 fused to the FLAG epitope showed histone deacetylase activity, which was inhibited by trichostatin A (TSA), a specific inhibitor of histone deacetylase. The null mutation of phd1 + resulted in a marked decrease in the total cellular histone deacetylase activity and an increase in the sensitivity to TSA. Although the phd1 disruptant showed no obvious defect in the mitotic cell cycle or mating, both homothallic haploid and heterothallic diploid cells failed to form spores in the absence of phd1 + . These results indicate that phd1 + encodes a histone deacetylase, which is involved in the meiotic cell cycle in S. pombe. z 1998 Federation of European Biochemical Societies.