During replicative cycle of retroviruses, the reverse-transcribed viral DNA is integrated into the host chromosome by the viral integrase enzyme. RNase H activity is associated with the reverse transcriptase. Endohydrolysis of RNA in RNA/DNA hybrids. Three different cleavage modes: 1. sequence-specific internal cleavage of RNA. Human immunodeficiency virus type 1 and Moloney murine leukemia virus enzymes prefer to cleave the RNA strand one nucleotide away from the RNA-DNA junction. 2. RNA 5'-end directed cleavage 13-19 nucleotides from the RNA end. 3. DNA 3'-end directed cleavage 15-20 nucleotides away from the primer terminus. 3'-end directed exonucleolytic cleavage of viral RNA-DNA hybrid. dUTP + H2O = diphosphate + dUMP + H(+) a 2'-deoxyribonucleoside 5'-triphosphate + DNA(n) = diphosphate + DNA(n+1) Cleavage sites that yield the mature proteins remain to be determined. Belongs to the retroviral Pol polyprotein family.