Yeast DNA repair proteins Rad6 and Rad18 form a heterodimer that has ubiquitin conjugating, DNA binding, and ATP hydrolytic activities

Veronique Bailly, Scott Lauder, Satya Prakash, Louise Prakash

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The RAD6 and RAD18 genes of Saccharomyces cerevisiae are required for postreplicative bypass of ultraviolet (UV)-damaged DNA and for UV mutagenesis. The RAD6 encoded protein is a ubiquitin conjugating enzyme, and RAD18 encodes a protein containing a RING finger motif and a nucleotide binding motif. Rad18 can be co-immunoprecipitated with Rad6, indicating that the two proteins exist in a complex in vivo. Here, we co-overproduce the two proteins using a yeast multicopy plasmid, purify the Rad6-Rad18 complex to near homogeneity, and show that the complex is heterodimeric. The Rad6-Rad18 heterodimer has ubiquitin conjugating activity, binds single-stranded DNA, and possesses single-stranded DNA-dependent ATPase activity. The Rad6-Rad18 complex provides the first example wherein a ubiquitin conjugating activity is physically associated with DNA binding and ATPase activities provided by an associated protein factor. The co-existence of these activities should provide the complex with the ability to recognize single-stranded DNA resulting from stalling of the replication machinery at DNA damage sites and to recognize the components of the DNA replication machinery for ubiquitination by Rad6.

Original languageEnglish (US)
Pages (from-to)23360-23365
Number of pages6
JournalJournal of Biological Chemistry
Issue number37
StatePublished - 1997


ASJC Scopus subject areas

  • Biochemistry

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