Unlocking Skin Cancer Prevention: How And-1 Protein Powers DNA Repair Against UV Damage

The Critical Role of And-1 in UV Damage Defense

Recent groundbreaking research published in Nature Communications has revealed the crucial function of the And-1 protein in protecting skin cells from UVB-induced damage that can lead to skin cancer. Scientists have discovered that And-1 coordinates with polymerase δ to regulate nucleotide excision repair (NER), the primary pathway responsible for fixing UV-induced DNA lesions. This discovery opens new avenues for understanding how our bodies naturally defend against skin cancer and potentially developing new preventive strategies.

The Critical Role of And-1 in UV Damage Defense
Direct Evidence: And-1 Accumulates at DNA Damage Sites
And-1 is Essential for Effective DNA Repair
Molecular Partnerships: How And-1 Coordinates Repair
And-1 Specifically Facilitates Polymerase δ Recruitment
Mechanistic Insights: How And-1 Enables Repair Complex Assembly
Phosphorylation Regulation: The ATR Connection
Functional Validation: Repair Synthesis Depends on And-1 Phosphorylation
Implications for Skin Cancer Prevention and Treatment

Direct Evidence: And-1 Accumulates at DNA Damage Sites

Through sophisticated immunofluorescence analysis, researchers demonstrated that And-1 directly migrates to sites of UV-induced DNA damage. When primary human epidermal keratinocytes were exposed to UVB radiation, creating localized DNA lesions, And-1 consistently co-localized with both cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts (6-4PPs) – the two primary types of DNA damage caused by UV exposure. This pattern held true across multiple cell types, including immortalized human keratinocytes and primary human fibroblast cells, confirming the universal importance of And-1 in the DNA damage response.

And-1 is Essential for Effective DNA Repair

The research team went beyond mere observation to demonstrate And-1’s functional importance. Using ELISA assays to measure repair efficiency, they found that cells depleted of And-1 showed significantly compromised ability to remove both CPDs and 6-4PPs following UVB exposure. The repair kinetics revealed that CPD removal was consistently slower than 6-4PP removal across all cell lines tested, consistent with previous studies. Most importantly, cells lacking And-1 showed increased sensitivity to UVB treatment, while restoring And-1 expression effectively rescued cell viability, confirming its protective role against UV-induced damage.

Molecular Partnerships: How And-1 Coordinates Repair

Mass spectrometry analysis uncovered that And-1 interacts with key NER factors, including DDB1 and POLD1/p125. Co-immunoprecipitation assays confirmed these interactions and showed they were significantly enhanced following UVB exposure. The timing of these interactions reveals a sophisticated coordination system: DDB1 rapidly accumulates at chromatin within minutes of UV exposure but diminishes within an hour, functioning in early damage recognition. In contrast, And-1 and p125 begin accumulating within 5-10 minutes but reach maximum levels much later – 4 hours for And-1 and 8 hours for p125 – indicating their role in later repair stages.

And-1 Specifically Facilitates Polymerase δ Recruitment

The research provides compelling evidence that And-1 specifically enables the recruitment of polymerase δ (p125) to damage sites. When researchers depleted And-1, the chromatin accumulation of p125 was significantly impaired, while DDB1 recruitment remained unaffected. Similarly, the co-localization of p125 with CPDs was compromised without And-1, and this defect was rescued by restoring And-1 expression. Interestingly, polymerase ε recruitment was unaffected by And-1 depletion, demonstrating the specificity of And-1 for polymerase δ-mediated repair.

Mechanistic Insights: How And-1 Enables Repair Complex Assembly

The study uncovered that And-1 facilitates p125 recruitment by enhancing its interaction with PCNA, a critical sliding clamp protein that coordinates DNA repair synthesis. UVB exposure normally increases p125-PCNA interaction, but this enhancement was significantly reduced in And-1-depleted cells and restored by And-1 re-expression. Additionally, And-1 interacts with p66, another essential component for p125 recruitment to damage sites, and And-1 depletion impaired p66’s localization to CPD lesions and chromatin association.

Phosphorylation Regulation: The ATR Connection

Researchers discovered that phosphorylation of And-1 at threonine 826 (T826) by the ATR kinase is crucial for its function in NER. UVB exposure significantly increased phosphorylated And-1 levels, and this phosphorylation was abolished by ATR inhibition. The phosphorylated form of And-1 co-localized with CPDs, and mutation of the T826 phosphorylation site prevented And-1 accumulation at damage sites. Most importantly, only wild-type And-1, not the T826A mutant, could restore p125 recruitment, p125-PCNA interaction, and repair synthesis capacity in And-1-depleted cells.

Functional Validation: Repair Synthesis Depends on And-1 Phosphorylation

Unscheduled DNA synthesis assays provided direct evidence that And-1 phosphorylation is essential for repair synthesis. Robust EdU incorporation occurred at UV-induced CPD lesions in control cells, but this repair synthesis was markedly reduced upon And-1 depletion. Only wild-type And-1, not the T826A phosphorylation-deficient mutant, could restore normal repair synthesis levels. Furthermore, the phospho-mimetic T826E mutant partially restored CPD removal even under ATR inhibition, demonstrating that phosphorylation is a key regulatory mechanism for And-1’s repair function.

Implications for Skin Cancer Prevention and Treatment

This comprehensive research establishes And-1 as a critical coordinator of the nucleotide excision repair pathway, specifically facilitating polymerase δ recruitment to UV damage sites through phosphorylation-dependent mechanisms. The findings provide crucial insights into how our cells maintain genomic stability against environmental UV exposure and suggest that enhancing And-1 function could represent a novel strategy for preventing UV-induced skin carcinogenesis. Understanding these molecular mechanisms opens possibilities for developing interventions that boost natural DNA repair capacity, potentially reducing skin cancer risk in high-exposure populations.

Key Findings Summary:

And-1 directly accumulates at UV-induced DNA damage sites
Essential for efficient removal of both CPDs and 6-4PPs
Specifically recruits polymerase δ to damage sites via PCNA interaction
Phosphorylation by ATR at T826 is crucial for function
Required for proper repair synthesis during nucleotide excision repair
Represents a potential target for skin cancer prevention strategies

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