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DNA polymerase eta is a Y family polymerase involved in translesion synthesis (TLS). Its action is initiated by simultaneous interaction between the PIP box in pol eta and PCNA and between the UBZ in pol eta and monoubiquitin attached to PCNA. Whereas monoubiquitination of PCNA is required for its interaction with pol eta during TLS, we now show that monoubiquitination of pol eta inhibits this interaction, preventing its functions in undamaged cells. Identification of monoubiquitination sites within pol eta nuclear localization signal (NLS) led to the discovery that pol eta NLS directly contacts PCNA, forming an extended pol eta-PCNA interaction surface. We name this the PCNA-interacting region (PIR) and show that its monoubiquitination is downregulated by various DNA-damaging agents. We propose that this mechanism ensures optimal availability of nonubiquitinated, TLS-competent pol eta after DNA damage. Our work shows how monoubiquitination can either positively or negatively regulate the assembly of a protein complex, depending on which substrates are targeted by ubiquitin.

Original publication

DOI

10.1016/j.molcel.2009.12.039

Type

Journal article

Journal

Mol Cell

Publication Date

12/02/2010

Volume

37

Pages

396 - 407

Keywords

Amino Acid Sequence, Cell Line, DNA Damage, DNA-Directed DNA Polymerase, Humans, Molecular Sequence Data, Mutagens, Nuclear Localization Signals, Proliferating Cell Nuclear Antigen, Sequence Alignment, Ubiquitination