C-anaphase in a case of acute nonlymphocytic leukemia

Radiation induces premature chromatid separation via the miR-142-3p/Bod1 pathway in carcinoma cells

Radiation-induced genomic instability plays a vital role in carcinogenesis. Bod1 is required for proper chromosome biorientation, and Bod1 depletion increases premature chromatid separation. MiR-142-3p influences cell cycle progression and inhibits proliferation and invasion in cervical carcinoma cells. We found that radiation induced premature chromatid separation and altered miR-142-3p and Bod1 expression in 786-O and A549 cells. Overexpression of miR-142-3p increased premature chromatid separation and G2/M cell cycle arrest in 786-O cells by suppressing Bod1 expression. We also found that either overexpression of miR-142-3p or knockdown of Bod1 sensitized 786-O and A549 cells to X-ray radiation. Overexpression of Bod1 inhibited radiation- and miR-142-3p-induced premature chromatid separation and increased resistance to radiation in 786-O and A549 cells. Taken together, these results suggest that radiation alters miR-142-3p and Bod1 expression in carcinoma cells, and thus contributes to early stages of radiation-induced genomic instability. Combining ionizing radiation with epigenetic regulation may help improve cancer therapies.

Epigenetic displacement of HP1 from heterochromatin by HIV-1 Vpr causes premature sister chromatid separation

Although pericentromeric heterochromatin is essential for chromosome segregation, its role in humans remains controversial. Dissecting the function of HIV-1-encoded Vpr, we unraveled important properties of heterochromatin during chromosome segregation. In Vpr-expressing cells, hRad21, hSgo1, and hMis12, which are crucial for proper chromosome segregation, were displaced from the centromeres of mitotic chromosomes, resulting in premature chromatid separation (PCS). Interestingly, Vpr displaced heterochromatin protein 1-α (HP1-α) and HP1-γ from chromatin. RNA interference (RNAi) experiments revealed that down-regulation of HP1-α and/or HP1-γ induced PCS, concomitant with the displacement of hRad21. Notably, Vpr stimulated the acetylation of histone H3, whereas p300 RNAi attenuated the Vpr-induced displacement of HP1-α and PCS. Furthermore, Vpr bound to p300 that was present in insoluble regions of the nucleus, suggesting that Vpr aberrantly recruits the histone acetyltransferase activity of p300 to chromatin, displaces HP1-α, and causes chromatid cohesion defects. Our study reveals for the first time centromere cohesion impairment resulting from epigenetic disruption of higher-order structures of heterochromatin by a viral pathogen.

Premature sister chromatid separation in HIV-1-infected peripheral blood lymphocytes

To investigate the mechanism of aneuploidy that is frequently observed in AIDS, we examined premature sister chromatid separation (PCS), a sign of genomic instability, in peripheral blood cells of HIV-1-infected individuals. PCS was found in all six HIV-1 individuals at a high incidence. When peripheral blood cells from healthy volunteers were infected with HIV-1 in vitro, the incidence of PCS increased. This suggests that HIV-1 infection causes PCS and has the potential to induce aneuploidy.