Nucleic Acids Research Advance Access originally published online on November 16, 2008
Nucleic Acids Research 2009 37(1):96-110; doi:10.1093/nar/gkn913
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Nucleic Acids Research, 2009, Vol. 37, No. 1 96-110
© 2008 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Nucleic Acid Enzymes |
Contributions of the two accessory subunits, RNASEH2B and RNASEH2C, to the activity and properties of the human RNase H2 complex
1Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda MD 20892, 2Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390 and 3Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, MO 63110, USA
*To whom correspondence should be addressed. Tel: +1 301 496 40 82; Fax: +1 301 496 02 43; Email: robert_crouch{at}nih.gov
Received September 12, 2008. Revised October 17, 2008. Accepted October 29, 2008.
Eukaryotic RNase H2 is a heterotrimeric enzyme. Here, we show that the biochemical composition and stoichiometry of the human RNase H2 complex is consistent with the properties previously deduced from genetic studies. The catalytic subunit of eukaryotic RNase H2, RNASEH2A, is well conserved and similar to the monomeric prokaryotic RNase HII. In contrast, the RNASEH2B and RNASEH2C subunits from human and Saccharomyces cerevisiae share very little homology, although they both form soluble B/C complexes that may serve as a nucleation site for the addition of RNASEH2A to form an active RNase H2, or for interactions with other proteins to support different functions. The RNASEH2B subunit has a PIP-box and confers PCNA binding to human RNase H2. Unlike Escherichia coli RNase HII, eukaryotic RNase H2 acts processively and hydrolyzes a variety of RNA/DNA hybrids with similar efficiencies, suggesting multiple cellular substrates. Moreover, of five analyzed mutations in human RNASEH2B and RNASEH2C linked to Aicardi-Goutières Syndrome (AGS), only one, R69W in the RNASEH2C protein, exhibits a significant reduction in specific activity, revealing a role for the C subunit in enzymatic activity. Near-normal activity of four AGS-related mutant enzymes was unexpected in light of their predicted impairment causing the AGS phenotype.
Present address: Yingming Zhao, Ben May Department of Cancer Research, The University of Chicago, 929 E. 57th Street, W430, Chicago, IL 60637, USA
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