Tetratricopeptide repeat factor XAB2 mediates the end resection step of homologous recombination

Abstract

We examined the influence of the tetratricopeptide repeat factor XAB2 on chromosomal break repair, and found that XAB2 promotes end resection that generates the 3′ ssDNA intermediate for homologous recombination (HR). Namely, XAB2 is important for chromosomal double-strand break (DSB) repair via two pathways of HR that require end resection as an intermediate step, end resection of camptothecin (Cpt)-induced DNA damage, and RAD51 recruitment to ionizing radiation induced foci (IRIF), which requires end resection. Furthermore, XAB2 mediates specific aspects of the DNA damage response associated with end resection proficiency: CtIP hyperphosphorylation induced by Cpt and BRCA1 IRIF. XAB2 also promotes histone acetylation events linked to HR proficiency. From truncation mutation analysis, the capacity for XAB2 to promote HR correlates with its ability to form a complex with ISY1 and PRP19, which show a similar influence as XAB2 on HR. This XAB2 complex localizes to punctate structures consistent with interchromatin granules that show a striking adjacent-localization to the DSB marker γH2AX. In summary, we suggest that the XAB2 complex mediates DNA damage response events important for the end resection step of HR, and speculate that its adjacent-localization relative to DSBs marked by γH2AX is important for this function.

A novel nuclear speckle factor, USP42, promotes homologous recombination repair by resolving DNA double-strand break induced R-loop

“…The efficiencies of HR were Z-score normalized, identifying several factors that potentially regulated HR together with a positive control (siCtIP) and factors already indicated to promote HR, such as XAB2 and ZMYND8 ( Fig. 1C) (30,31). Furthermore, the DR-GFP assay was carried out with two individual siRNAs targeting WDR5, DHX9, GTF3C2 and USP42, verifying the results of the initial screen and identifying these factors as novel HR regulatory proteins ( Fig.…”

XAB2 prevents abortive recombinational repair of replication-associated DNA double-strand breaks and its loss is synthetic lethal with RAD52 inhibition

“…XAB2 is important for the repair of DSBs associated with O 6 -meG lesions left unrepaired by MGMT. Given the proposed role of XAB2 in promoting HR [38], we first examined the impact of XAB2 depletion on the repair of DSBs induced by TMZ. We treated control and XAB2-depleted NCH644 cells with TMZ for 2 h and visualizedH2AX foci, a DSB marker, by indirect immunofluorescence (IF) after a 72 h recovery period in drug-free medium, corresponding to ~2 cell cycles after DNA damage induction.…”

“…Regulation of end resection also involves p53 binding protein 1 (53BP1), effector molecules [34] and the helicase HELB [35]. Recently, several splicing factors have been involved in DNA end resection, including ZNF830 [36], Aquarius [37] and XAB2 [37,38], by mechanisms that remain to be elucidated.…”

XAB2 functions in mitotic cell cycle progression via transcriptional regulation of CENPE

“…Cells were treated with CENPE siRNA or XAB2 siRNA for analysis 24 or 55 h, respectively, after transfection. CENPE siRNA and XAB2 siRNA were previously reported, 22, 50 non-target siRNA (RiboBio, China) was used as negative control. The siRNA sequences are as follows: CENPE siRNA (5′-CCACUAGAGUUGAAAGAUAdTdT-3′), XAB2-siRNA-1 (5′-CCAAUUCUCUGUCAAAUGCdTdT-3′), XAB2-siRNA-2 (5′-ACGCAGCACUCUCGAAUUUdTdT-3′).…”

“…21 Most recently, XAB2 has been reported to regulate the end resection step during homologous recombination repair of chromosomal double-strand breaks. 22 Thus, XAB2 is an important multifunctional protein.…”