BLM helicase-dependent transport of p53 to sites of stalled DNA replication forks modulates homologous recombination

Abstract

Diverse functions, including DNA replication, recombination and repair, occur during S phase of the eukaryotic cell cycle. It has been proposed that p53 and BLM help regulate these functions. We show that p53 and BLM accumulated after hydroxyurea (HU) treatment, and physically associated and co-localized with each other and with RAD51 at sites of stalled DNA replication forks. HU-induced relocalization of BLM to RAD51 foci was p53 independent. However, BLM was required for efficient localization of either wild-type or mutated (Ser15Ala) p53 to these foci and for physical association of p53 with RAD51. Loss of BLM and p53 function synergistically enhanced homologous recombination frequency, indicating that they mediated the process by complementary pathways. Loss of p53 further enhanced the rate of spontaneous sister chromatid exchange (SCE) in Bloom syndrome (BS) cells, but not in their BLM-corrected counterpart, indicating that involvement of p53 in regulating spontaneous SCE is BLM dependent. These results indicate that p53 and BLM functionally interact during resolution of stalled DNA replication forks and provide insight into the mechanism of genomic fidelity maintenance by these nuclear proteins.

JAK2V617F negatively regulates p53 stabilization by enhancing MDM2 via La expression in myeloproliferative neoplasms

“…These experiments were reproduced in independently derived cell lines (data not shown). Immunofluorescence analysis of [pS 15 ]-p53 demonstrated its nuclear localization in Ba/F3-EPOR and Ba/F3-EPOR-JAK2 wt that was strongly inhibited in Ba/F3-EPOR-JAK2 V617F cells (Sengupta et al, 2003) (Figure 1d). Thus, JAK2 V617F expression appeared to reduce p53 stabilization and phosphorylation upon DNA damage.…”

HIV-1 Vpr induces ATM-dependent cellular signal with enhanced homologous recombination

“…It has been reported that p53 associates with several proteins including BLM, BRCA1, BRCA2, Rad52 and RPA (Yamaguchi-Iwai Marmorstein et al, 1998;Zhang et al, 1998;Linke et al, 2003;Sengupta et al, 2003) and inhibits the Rad51-dependent HR (Cromie et al, 2001;Linke et al, 2003). When DSBs were induced, the association of p53 and Rad51 was prevented by an unknown mechanism.…”

Suppression of replication fork progression in low-dose-specific p53-dependent S-phase DNA damage checkpoint

“…p53 was shown to respond to the replication block induced by aphidicolin (Gottifredi et al, 2001;Nayak and Das, 2002) and colocalized with BLM, Rad51 and 53BP1 at the sites of stalled DNA replication fork (Sengupta et al, 2003(Sengupta et al, , 2004. p53 also accumulated during S-phase in Cdc7À/À ES cells with defective replication origin firing (Kim et al, 2002).…”