EVIDENCE FOR A PHYSICAL INTERACTION BETWEEN THE ESCHERICHIA-COLI METHYL-DIRECTED MISMATCH REPAIR PROTEINS MUTL AND UVRD

UvrD (DNA helicase II) is an essential component of two major DNA repa ir pathways in Escherichia coli: methyl-directed mismatch repair and U vrABC-mediated nucleotide excision repair, In addition, it has an unde fined role in the RecF recombination pathway and possibly in replicati on. In an effort to better understand the role of UvrD in these variou s aspects of DNA metabolism, a yeast two-hybrid screen was used to sea rch for interacting protein partners. Screening of an E. coli genomic library revealed a potential interaction between UvrD and MutL, a comp onent of the methyl-directed mismatch repair pathway, The interaction was confirmed by affinity chromatography using purified proteins, Dele tion analysis demonstrated that the C-terminal 218 amino acids (residu es 398-615) of MutL were sufficient to produce the two-hybrid interact ion with UvrD, On the other hand, both the N- and C-termini of UvrD we re required for interaction with MutL, The implications of this intera ction for the mismatch repair mechanism are discussed.