title: Nuclease mechanism of the avian retrovirus pp32 endonuclease.
abstract: In vivo, the inferred circular retrovirus DNA precursor to the provirus contains two long terminal repeats (LTRs) in tandem. We studied the site-specific nicking of supercoiled DNA that contains tandem copies of avian retrovirus LTR DNA in vitro by using purified avian myeloblastosis virus pp32 endonuclease, Mg2+, and viral DNA substrates containing different LTR circle junction sequences. The results confirmed our previous observation that the pp32 protein generates two nicks, one in either viral DNA strand, each 2 nucleotides from the circle junction site. The specificity of nicking by pp32 was unchanged over an eight-fold range of protein concentration and with different avian retrovirus LTR circle junction substrates. These data are consistent with models which propose a role for the endonuclease in removal of two nucleotides from the LTR termini on integration of viral DNA in vivo.
mesh_terms: D001354:Avian Leukosis Virus / Q000201:enzymology*; D009189:Avian Myeloblastosis Virus / Q000201:enzymology*; D004279:DNA, Viral / Q000032:analysis; D004720:Endonucleases / Q000494:pharmacology*; D008345:Manganese / Q000494:pharmacology; D010750:Phosphoproteins / Q000494:pharmacology*; D012091:Repetitive Sequences, Nucleic Acid
chemical_list: D004279:DNA, Viral; D010750:Phosphoproteins; D008345:Manganese; D004720:Endonucleases