The protein kinase BRAF activates MAP kinase signaling pathways that regulate cell proliferation. The oncogenic BRAF gene is mutated up to 70% of melanoma, the deadliest form of skin cancer. Interestingly, BRAF mutations predominantly occur at codon 600 (GTG) and are T-to-A transversions, leading to BRAF V600E mutations. While solar ultraviolet (UV) irradiation is the prime suspect for melanoma, the identity of DNA lesion responsible for the dominant BRAF mutations is unknown, limiting our understanding of melanoma-genesis mechanisms. This knowledge gap prompted us to search for DNA lesion driving the BRAF V600E mutagenesis. To gain mechanistic insights into the solar rays-induced BRAF muta...

Read More

The protein kinase BRAF activates MAP kinase signaling pathways that regulate cell proliferation. The oncogenic BRAF gene is mutated up to 70% of melanoma, the deadliest form of skin cancer. Interestingly, BRAF mutations predominantly occur at codon 600 (GTG) and are T-to-A transversions, leading to BRAF V600E mutations. While solar ultraviolet (UV) irradiation is the prime suspect for melanoma, the identity of DNA lesion responsible for the dominant BRAF mutations is unknown, limiting our understanding of melanoma-genesis mechanisms. This knowledge gap prompted us to search for DNA lesion driving the BRAF V600E mutagenesis. To gain mechanistic insights into the solar rays-induced BRAF mutations, we hypothesized that the BRAF mutations are triggered by UV-induced DNA interstrand cross-links (ICLs). Our preliminary studies showed that UV irradiation of DNA efficiently generated A-T ICLs in vitro in the GTG sequence context. These findings are significant as A-T ICLs are novel photoproducts and mark the first characterized example of UV-induced ICLs. Our hypothesis is that solar rays-induced ICLs contribute to the BRAF mutations and melanoma genesis. The goal of this proposal is to elucidate the structures and biological consequences of solar rays-induced ICLs and establish "DNA damage-mediated mutagenesis" in BRAF V600E mutations. The success of the proposed projects will generate detailed information on the cellular levels, structures, mutagenic properties, cellular responses, and repair mechanisms of the long-overlooked solar rays-induced ICLs. This will provide critical insights into the mechanisms by which photo-induced ICLs promote mutations and skin cancers. Establishing the etiologic relevance of UVB irradiation in BRAF mutagenesis may advance our understanding of the melanoma-genesis mechanism(s), thereby helping with devising strategies for prevention, early detection, and treatment of this malignant disease.

Read Less