RNase H1 generally processes the RNA- DNA hybrids through non specific interaction between HBD and the ds RNA/DNA hybrid. There are no direct protein- protein interactions between the hybrid and HBD of RNase H1. The DNA binding region is highly conserved compared to RNA binding region and the Kd for RNA/DNA hybrid is less compared to ds RNA than to that of ds DNA . HBD increases the processivity of RNase H1 and mutations in RNA binding region is tolerated compared to DBR. The RNA interacts between ɑ2 and β3 region with in the loop and with the protein in shallower minor groove. The HBD is similar to that of RNA binding domains of RNases like dicer, RNase III. RNase H1 and H2 and are involved in removal of R-loops. But RNase H2 is involved in post replicational removal of R loops and whereas RNase H1 R loop repair is not restricted to particular phase of cell cycle. RNase H2 also protects from toxic sensitivity of Methyl Methane sulfonate and from mismatched errors of Mono ribonucleotide excision repair and is not dependent on activity of TOPO1. Double mutants in RNase H2 are not tolerant but it promotes growth similar to single mutants.