title: Substrate specificity of the MUS81-EME2 structure selective endonuclease.
abstract: MUS81 plays important cellular roles in the restart of stalled replication forks, the resolution of recombination intermediates and in telomere length maintenance. Although the actions of MUS81-EME1 have been extensively investigated, MUS81 is the catalytic subunit of two human structure-selective endonucleases, MUS81-EME1 and MUS81-EME2. Little is presently known about the activities of MUS81-EME2. Here, we have purified MUS81-EME2 and compared its activities with MUS81-EME1. We find that MUS81-EME2 is a more active endonuclease than MUS81-EME1 and exhibits broader substrate specificity. Like MUS81-EME1, MUS81-EME2 cleaves 3'-flaps, replication forks and nicked Holliday junctions, and exhibits limited endonuclease activity with intact Holliday junctions. In contrast to MUS81-EME1, however, MUS81-EME2 cuts D-loop recombination intermediates and in so doing disengages the D-loop structure by cleaving the 3'-invading strand. Additionally, MUS81-EME2 acts on 5'-flap structures to cleave off a duplex arm, in reactions that cannot be promoted by MUS81-EME1. These studies suggest that MUS81-EME1 and MUS81-EME2 exhibit similar and yet distinct DNA structure selectivity, indicating that the two MUS81 complexes may promote different nucleolytic cleavage reactions in vivo.
authors.affiliation: London Research Institute, Cancer Research UK, Clare Hall Laboratories, South Mimms, Herts EN6 3LD, UK.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Pepe
authors.forename: Stephen C
authors.initials: SC
authors.lastname: West
mesh_terms: D000595:Amino Acid Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004706:Endodeoxyribonucleases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004720:Endonucleases / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000378:metabolism; D011995:Recombination, Genetic; D016415:Sequence Alignment; D013379:Substrate Specificity
chemical_list: D004268:DNA-Binding Proteins; D020033:Protein Isoforms; C000588977:EME2 protein, human; C000588978:EME2B protein, human; C507947:Eme1 protein, human; D004706:Endodeoxyribonucleases; D004720:Endonucleases; C498772:MUS81 protein, human