The function of RNASEH1 (ribonuclease H1, ENSG00000171865) is as follows. Endonuclease that specifically degrades the RNA of RNA-DNA hybrids (PubMed:10497183). Plays a role in RNA polymerase II (RNAp II) transcription termination by degrading R-loop RNA-DNA hybrid formation at G-rich pause sites located downstream of the poly(A) site and behind the elongating RNAp II (PubMed:21700224). {ECO:0000269|PubMed:10497183, ECO:0000269|PubMed:21700224}.