Abstract:
:Studies of phage lambda in vivo have indicated that its own recombination enzymes, beta protein and lambda exonuclease, are capable of catalyzing two dissimilar pathways of homologous recombination that are widely distributed in nature: single-strand annealing and strand invasion. The former is an enzymatic splicing of overlapping ends of broken homologous DNA molecules, whereas the latter is characterized by the formation of a three-stranded synaptic intermediate and subsequent strand exchange. Previous studies in vitro have shown that beta protein has annealing activity, and that lambda exonuclease, acting on branched substrates, can produce a perfect splice that requires only ligation for completion. The present study shows that beta protein can initiate strand invasion in vitro, as evidenced both by the formation of displacement loops (D-loops) in superhelical DNA and by strand exchange between colinear single-stranded and double-stranded molecules. Thus, beta protein can catalyze steps that are central to both strand annealing and strand invasion pathways of recombination. These observations add beta protein to a set of diverse proteins that appear to promote recognition of homology by a unitary mechanism governed by the intrinsic dynamic properties of base pairs in DNA.
journal_name
Proc Natl Acad Sci U S Aauthors
Rybalchenko N,Golub EI,Bi B,Radding CMdoi
10.1073/pnas.0408046101keywords:
subject
Has Abstractpub_date
2004-12-07 00:00:00pages
17056-60issue
49eissn
0027-8424issn
1091-6490pii
0408046101journal_volume
101pub_type
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