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J Biol Chem. 2019 Apr 12;294(15):6073-6081. doi: 10.1074/jbc.RA119.007925. Epub 2019 Mar 6.

Human DNA polymerase η has reverse transcriptase activity in cellular environments.

Author information

1
From the Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146 and.
2
Department of Chemistry, University of California, Riverside, Riverside, California 92521.
3
From the Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146 and f.guengerich@vanderbilt.edu.

Abstract

Classical DNA and RNA polymerase (pol) enzymes have defined roles with their respective substrates, but several pols have been found to have multiple functions. We reported previously that purified human DNA pol η (hpol η) can incorporate both deoxyribonucleoside triphosphates (dNTPs) and ribonucleoside triphosphates (rNTPs) and can use both DNA and RNA as substrates. X-ray crystal structures revealed that two pol η residues, Phe-18 and Tyr-92, behave as steric gates to influence sugar selectivity. However, the physiological relevance of these phenomena has not been established. Here, we show that purified hpol η adds rNTPs to DNA primers at physiological rNTP concentrations and in the presence of competing dNTPs. When two rATPs were inserted opposite a cyclobutane pyrimidine dimer, the substrate was less efficiently cleaved by human RNase H2. Human XP-V fibroblast extracts, devoid of hpol η, could not add rNTPs to a DNA primer, but the expression of transfected hpol η in the cells restored this ability. XP-V cell extracts did not add dNTPs to DNA primers hybridized to RNA, but could when hpol η was expressed in the cells. HEK293T cell extracts could add dNTPs to DNA primers hybridized to RNA, but lost this ability if hpol η was deleted. Interestingly, a similar phenomenon was not observed when other translesion synthesis (TLS) DNA polymerases-hpol ι, κ, or ζ-were individually deleted. These results suggest that hpol η is one of the major reverse transcriptases involved in physiological processes in human cells.

KEYWORDS:

DNA damage; DNA enzyme; DNA pol eta; DNA polymerase; DNA replication; DNA transcription; RNA polymerase; reverse transcription; translesion synthesis (TLS) enzyme

PMID:
30842261
PMCID:
PMC6463694
[Available on 2020-04-12]
DOI:
10.1074/jbc.RA119.007925

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