| Budget Amount *help |
¥36,700,000 (Direct Cost: ¥36,700,000)
Fiscal Year 2004: ¥7,000,000 (Direct Cost: ¥7,000,000)
Fiscal Year 2003: ¥7,300,000 (Direct Cost: ¥7,300,000)
Fiscal Year 2002: ¥9,000,000 (Direct Cost: ¥9,000,000)
Fiscal Year 2001: ¥8,400,000 (Direct Cost: ¥8,400,000)
Fiscal Year 2000: ¥5,000,000 (Direct Cost: ¥5,000,000)
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| Research Abstract |
Premature sister chromatid separation (PCS), a hallmark of genomic instability, was found in all six HIV-1 individuals at a high incidence (2.1-9.0%), whereas it was rarely detected in healthy volunteers (<1.0%). The incidence of PCS seemed to be correlated with the number of HIV-1 RNA copies. When blood cells from healthy volunteers were infected with HIV-1, the incidence of PCS increased from 1.23±0.22% to 9.90±1.92%. On the other hand, a mutant virus lacking of Vpr, an accessory gene off HIV-1, did not increase PCS. To show direct linkage between Vpr and PCS, metaphase spreads prepared under Vpr expression were examined. About half of analyzed cells contained PCS. These data indicate that Vpr is responsible for PCS. Immunohistochemical analysis revealed that Vpr localizes to condensed chromosomes. Furthermore, p300, a histone acetyl transferase (HAT) known as a Vpr binding partner, co-localized with Vpr especially in the region around centromere, and the expression of suv39hl, histo
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ne methyl transferase, was quickly decreased after Vpr expression. Consistently, histone H3 of the entire condensed chromosomes was highly acetylated at lysine 9 (H3-K9). Vpr eliminates heterochromatin protein 1 (HP1α) from condensed chromosomes, and kinetochore components such as RAD21/SCC1, INCENP, Aurora-B, and CENP-F were also repressed by Vpr. By contrast, Vpr forms a complex with CENP-A. Given that methylation of histone H3-K9 is required for direct association of HP1 with chromatin, and that HP la is required for organization of kinetochore components responsible for proper segregation of sister chromatids, our observation well explains the mechanism of Vpr-induced aneuploidy. Elimination of RAD21/SCC1 subsequently induces PCS with mis-segregation of chromosomes. The introduction of p300 siRNA blocked Vpr-induced dissociation of HP lα from -chromosomes and reduced the frequency of PCS, further supporting a notion that histone acetylation by Vpr with p300 induces unbalanced segregation of chromosomes. It is speculated that Vpr-induced genomic instability is involved in high incidence of AIDS-related malignant tumors. Further study is required to clarify a role of such Vpr activity in HIV-1 infection and/or viral replication. Less
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