Cell Cycle Arrest and Apoptosis

Abstract

The HIV-1 accessory gene vpr encodes a conserved 96-amino acid protein that is necessary and sufficient for the HIV-1-induced block of cellular proliferation and induction of apoptosis. Expression of vpr in CD4.sup.+ lymphocytes results in G2 arrest, followed by apoptosis. ATR, as a cellular factor that mediates Vpr-induced cell cycle arrest, is required for activation of the Breast Cancer-Associated Protein-1 (BRCA1). In addition, the Growth Arrest and DNA Damage protein (GADD45) is upregulated by Vpr in an ATR-dependent manner. Posttranscriptional silencing of either ATR or GADD45 leads to nearly complete suppression of the pro-apoptotic and/or cell cycle arrest effect of Vpr.

1 . A compound comprising Vpr or a functional fragment thereof linked to an adipose tissue targeting moiety. 
     
     
         2 . The compound of  claim 1 , wherein the targeting moiety comprises SEQ ID NO:1. 
     
     
         3 . A method of treating obesity in a subject, the method comprising administering a compound according to  claim 1  to the subject. 
     
     
         4 . A method of inducing apoptosis in a subject, the method comprising:
 introducing Vpr and BRAC1, or a functional fragment thereof to a subject; and   inducing apoptosis in the subject.   
     
     
         5 . The method according to  claim 4 , wherein the subject has been diagnosed as having a mutation in a BRAC1 gene. 
     
     
         6 . A method of inducing GADD45, the method comprising administering Vpr, ATR or a functional fragment thereof to a subject. 
     
     
         7 . A method of activating BRAC1, the method comprising administering Vpr, ATR or a functional fragment thereof to a subject. 
     
     
         8 . The method according to  claim 4 , wherein the subject is a mammal. 
     
     
         9 . The method according to  claim 4 , wherein the subject comprises a cell culture system. 
     
     
         10 . A method of inducing G2 cell cycle arrest, the method comprising:
 administering Vpr, activated ATP, or a functional fragment thereof to a subject;   inducing activation of BRAC1 or RAD17; and   arresting cell cycle progression in G2.   
     
     
         11 . A method of screening a compound for apoptotic activity, the method comprising:
 administering a compound to a subject having an ATR protein and a BRAC1 protein;   assaying for ATR dependent phosphorylation of BRAC1; and   identifying the compound as inducing or inhibiting apoptosis.   
     
     
         12 . The method according to  claim 11 , wherein assaying for ATR dependent phosphorylation of BRACT comprises assaying for phosphorylation at serine 1423 of BRAC1. 
     
     
         13 . The method according to  claim 11 , wherein assaying for ATR dependent phosphorylation of BRAC1 comprises knocking down ATR expression. 
     
     
         14 . The method according to  claim 12 , further comprising culturing the subject. 
     
     
         15 . The method according to  claim 11 , wherein administering the compound to the subject comprises administering the compound to an animal model for a disease state. 
     
     
         16 . The method according to  claim 14 , further comprising introducing Vpr into the subject and screening the compound for inhibition of apoptosis. 
     
     
         17 . The method according to  claim 14 , further comprising comparing the compound to Vpr-induced apoptosis. 
     
     
         18 . The method according to  claim 6 , wherein the subject is a mammal. 
     
     
         19 . The method according to  claim 7 , wherein the subject is a mammal. 
     
     
         20 . The method according to  claim 4 , wherein the subject c comprises a cell culture system.