TY - JOUR
T1 - A novel DDB2 mutation causes defective recognition of UV-induced DNA damages and prevalent equine squamous cell carcinoma
AU - Chen, Lu
AU - Bellone, Rebecca R.
AU - Wang, Yan
AU - Singer-Berk, Moriel
AU - Sugasawa, Kaoru
AU - Ford, James M.
AU - Artandi, Steven E.
N1 - Funding Information:
The baculovirus-expression construct is a generous gift from Kaoru Sugasawa (Kobe University, Japan). The troubleshooting of the immunostaining procedure received invaluable helps from Adam Freund (Calico inc.). We also thank the discussions and suggestions from labs of James Ford and Gil Chu (Division of Oncology, Stanford University), and assistance from Margo Crausaz (UC-Davis). This work was supported by NIH (AG056575 and CA197563 to S.E.A.). L.C. was supported by a Stanford Cancer Institute Fellowship Award. This work was supported in part by the UC-Davis Center for Equine Health (#16-06) with funds provided by the State of California Pari-Mutuel Fund and contributions by private donors.
PY - 2021/1
Y1 - 2021/1
N2 - Squamous cell carcinoma (SCC) occurs frequently in the human Xeroderma Pigmentosum (XP) syndrome and is characterized by deficient UV-damage repair. SCC is the most common equine ocular cancer and the only associated genetic risk factor is a UV-damage repair protein. Specifically, a missense mutation in horse DDB2 (T338M) was strongly associated with both limbal SCC and third eyelid SCC in three breeds of horses (Halflinger, Belgian, and Rocky Mountain Horses) and was hypothesized to impair binding to UV-damaged DNA. Here, we investigate DDB2-T338M mutant's capacity to recognize UV lesions in vitro and in vivo, together with human XP mutants DDB2-R273H and -K244E. We show that the recombinant DDB2-T338M assembles with DDB1, but fails to show any detectable binding to DNA substrates with or without UV lesions, due to a potential structural disruption of the rigid DNA recognition β-loop. Consistently, we demonstrate that the cellular DDB2-T338M is defective in its recruitment to focally radiated DNA damages, and in its access to chromatin. Thus, we provide direct functional evidence indicating the DDB2-T338M recapitulates molecular defects of human XP mutants, and is the causal loss-of-function allele that gives rise to equine ocular SCCs. Our findings shed new light on the mechanism of DNA recognition by UV-DDB and on the initiation of ocular malignancy.
AB - Squamous cell carcinoma (SCC) occurs frequently in the human Xeroderma Pigmentosum (XP) syndrome and is characterized by deficient UV-damage repair. SCC is the most common equine ocular cancer and the only associated genetic risk factor is a UV-damage repair protein. Specifically, a missense mutation in horse DDB2 (T338M) was strongly associated with both limbal SCC and third eyelid SCC in three breeds of horses (Halflinger, Belgian, and Rocky Mountain Horses) and was hypothesized to impair binding to UV-damaged DNA. Here, we investigate DDB2-T338M mutant's capacity to recognize UV lesions in vitro and in vivo, together with human XP mutants DDB2-R273H and -K244E. We show that the recombinant DDB2-T338M assembles with DDB1, but fails to show any detectable binding to DNA substrates with or without UV lesions, due to a potential structural disruption of the rigid DNA recognition β-loop. Consistently, we demonstrate that the cellular DDB2-T338M is defective in its recruitment to focally radiated DNA damages, and in its access to chromatin. Thus, we provide direct functional evidence indicating the DDB2-T338M recapitulates molecular defects of human XP mutants, and is the causal loss-of-function allele that gives rise to equine ocular SCCs. Our findings shed new light on the mechanism of DNA recognition by UV-DDB and on the initiation of ocular malignancy.
KW - Chromatin association
KW - Disease mutations
KW - Equine genetics
KW - Localized UV irradiation
KW - Squamous cell carcinoma
KW - UV-DDB
KW - Xeroderma pigmentosum
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U2 - 10.1016/j.dnarep.2020.103022
DO - 10.1016/j.dnarep.2020.103022
M3 - Article
C2 - 33276309
AN - SCOPUS:85097059864
VL - 97
JO - DNA Repair
JF - DNA Repair
SN - 1568-7864
M1 - 103022
ER -