title: The over-expression of the β2 catalytic subunit of the proteasome decreases homologous recombination and impairs DNA double-strand break repair in human cells.
abstract: By a human cDNA library screening, we have previously identified two sequences coding two different catalytic subunits of the proteasome which increase homologous recombination (HR) when overexpressed in the yeast Saccharomyces cerevisiae. Here, we investigated the effect of proteasome on spontaneous HR and DNA repair in human cells. To determine if the proteasome has a role in the occurrence of spontaneous HR in human cells, we overexpressed the β2 subunit of the proteasome in HeLa cells and determined the effect on intrachromosomal HR. Results showed that the overexpression of β2 subunit decreased HR in human cells without altering the cell proteasome activity and the Rad51p level. Moreover, exposure to MG132 that inhibits the proteasome activity reduced HR in human cells. We also found that the expression of the β2 subunit increases the sensitivity to the camptothecin that induces DNA double-strand break (DSB). This suggests that the β2 subunit has an active role in HR and DSB repair but does not alter the intracellular level of the Rad51p.
authors.affiliation: Laboratorio di Terapia Genica e Molecolare, Istituto di Fisiologia Clinica CNR, Area della Ricerca CNR Via Moruzzi 1, 56125 Pisa, Italy.
authors.forename: Anita
authors.initials: A
authors.lastname: Collavoli
authors.forename: Laura
authors.initials: L
authors.lastname: Comelli
authors.forename: Tiziana
authors.initials: T
authors.lastname: Cervelli
authors.forename: Alvaro
authors.initials: A
authors.lastname: Galli
mesh_terms: D020134:Catalytic Domain / Q000235:genetics; D045744:Cell Line, Tumor; D053903:DNA Breaks, Double-Stranded; D004249:DNA Damage; D004260:DNA Repair / Q000235:genetics*; D006367:HeLa Cells / Q000378:metabolism; D006801:Humans; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D051135:Rad51 Recombinase / Q000378:metabolism*; D011995:Recombination, Genetic / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D014162:Transfection
chemical_list: D029701:Saccharomyces cerevisiae Proteins; D051135:Rad51 Recombinase; C561469:PSMB2 protein, human; D046988:Proteasome Endopeptidase Complex