A Kinase-Independent Function of c-Abl in Promoting Proteolytic Destruction of Damaged DNA Binding Proteins

Abstract

Damaged DNA binding proteins (DDBs) play a critical role in the initial recognition of UV-damaged DNA and mediate recruitment of nucleotide excision repair factors. Previous studies identified DDB2 as a target of the CUL-4A ubiquitin ligase. However, the biochemical mechanism governing DDB proteolysis and its underlying physiological function in the removal of UV-induced DNA damage are largely unknown. Here, we report that the c-Abl nonreceptor tyrosine kinase negatively regulates the repair of UV-induced photolesions on genomic DNA. Biochemical studies revealed that c-Abl promotes CUL-4A-mediated DDB ubiquitination and degradation in a manner that does not require its tyrosine kinase activity both under normal growth conditions and following UV irradiation. Moreover, c-Abl activates DDB degradation in part by alleviating the inhibitory effect of CAND1/TIP120A on CUL-4A. These results revealed a kinase-independent function of c-Abl in a ubiquitin-proteolytic pathway that regulates the damage recognition step of nucleotide excision repair.

Other Proteins Interacting with XP Proteins

“…18,21 Along with its role in transcriptional repression, XPE interacts with the Cullin4-ROC1-COP9 signalsome, which is part of the E3 ubiquitin ligase complex. 22,23 This pathway mediates 26S proteosome, degradation of ubiquitinylated proteins, and the interaction with XPE may serve to modulate protein degradation in response to UV irradiation. 18,24 Recently, XPE was found to interact with c-Abl tyrosine kinase and this interaction has been linked to modulation of Cullin4 targeting of XPE for degradation by the 26S proteosome following UV irradiation.…”

“…18,24 Recently, XPE was found to interact with c-Abl tyrosine kinase and this interaction has been linked to modulation of Cullin4 targeting of XPE for degradation by the 26S proteosome following UV irradiation. 22 XPA, a 32 kDa zinc metalloprotein, is the sole recognition factor required for both GG-NER and TG-NER activities and is believed to play a role in verification of DNA damage. 25,26 To date, the only known function for the XPA protein is in mediating NER and its protein interaction partners are limited primarily to factors required for damage removal.…”

“…22 XPD is part of the Cdk Activating Complex (CAK) component of TFIIH containing the additional subunits cdk7, cyclin H, and MAT1. XPD is bound to the CAK complex via an interaction with the coiled-coil region of the MAT1 subunit.…”

“…[45][46][47][48][49] XPB, a 90 kDa protein, is a 3′→5′ ATP hydrolysis-driven helicase although it has much weaker activity compared to that of XPD. 22 However, mutations in XPB are among the most rare in XP indicating XPB plays an extremely critical role in both NER and transcription. 50 In accordance with this observation, XPB interacts with a variety of different repair and transcription factors and it is these interactions, not XPB's helicase activity, that are critical for TFIIH activity.…”

“…22 p8 stimulates the helicase activity of both XPB (through direct interaction) and XPD (via interaction through p44) to promote DNA strand opening, a step necessary for assembly of pre-incision complexes. 22 The C-terminal of XPB can be phosphorylated by an as yet unidentified PP2A-related protein kinase and this phosphorylation is essential for the 5′ incision by XPG. 54 Another critical interaction of XPB is that with hSUG1, a component of the 26S proteosome.…”