Acquired Immunodeficiency Syndrome: Ishizaka Y

Nakai-Murakami C, Ishizaka Y. · Department of Intractable Diseases, International Medical Center of Japan, Tokyo. · Seikagaku. · Pubmed #17243638 No free full text.

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Tachiwana H, Shimura M, Nakai-Murakami C, Tokunaga K, Takizawa Y, Sata T, Kurumizaka H, Ishizaka Y. · Graduate School of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, 169-8555 Tokyo, Japan. · Cancer Res. · Pubmed #16423988 links to  free full text

Abstract: Recent observations imply that HIV-1 infection induces chromosomal DNA damage responses. However, the precise molecular mechanism and biological relevance are not fully understood. Here, we report that HIV-1 infection causes double-strand breaks in chromosomal DNA. We further found that Vpr, an accessory gene product of HIV-1, is a major factor responsible for HIV-1-induced double-strand breaks. The purified Vpr protein promotes double-strand breaks when incubated with isolated nuclei, although it does not exhibit endonuclease activity in vitro. A carboxyl-terminally truncated Vpr mutant that is defective in DNA-binding activity is less capable of Vpr-dependent double-strand break formation in isolated nuclei. The data suggest that double-strand breaks induced by Vpr depend on its DNA-binding activity and that Vpr may recruit unknown nuclear factor(s) with positive endonuclease activity to chromosomal DNA. This is the first direct evidence that Vpr induces double-strand breaks in HIV-1-infected cells. We discuss the possible roles of Vpr-induced DNA damage in HIV-1 infection and the involvement of Vpr in further acquired immunodeficiency syndrome-related tumor development.

Shimura M, Tanaka Y, Nakamura S, Minemoto Y, Yamashita K, Hatake K, Takaku F, Ishizaka Y. · Department of Intractable Diseases, International Medical Center of Japan, Shinjuku-ku, Tokyo. · FASEB J. · Pubmed #10094923 links to  free full text

Abstract: Vpr, an accessory gene of HIV-1, induces cell cycle abnormality with accumulation at G2/M phase and increased ploidy. Since abnormality of mitotic checkpoint control provides a molecular basis of genomic instability, we studied the effects of Vpr on genetic integrity using a stable clone, named MIT-23, in which Vpr expression is controlled by the tetracycline-responsive promoter. Treatment of MIT-23 cells with doxycycline (DOX) induced Vpr expression with a giant multinuclear cell formation. Increased micronuclei (MIN) formation was also detected in these cells. Abolishment of Vpr expression by DOX removal induced numerous asynchronous cytokinesis in the multinuclear cells with leaving MIN in cytoplasm, suggesting that the transient Vpr expression could cause genetic unbalance. Consistent with this expectation, MIT-23 cells, originally pseudodiploid cells, became aneuploid after repeated expression of Vpr. Experiments using deletion mutants of Vpr revealed that the domain inducing MIN formation as well as multinucleation was located in the carboxy-terminal region of Vpr protein. These results suggest that Vpr induces genomic instability, implicating the possible role in the development of AIDS-related malignancies.