What process is directly activated by UV exposure in skin cells?

What process is directly activated by UV exposure in skin cells?

• A. Activation of ribosome synthesis.
• B. Activation of transcription factors that increase melanin production.
• C. Degradation of DNA.
• D. Blockade of protein synthesis.

Answer: (B)

UV exposure in skin cells sets off a signaling cascade that ultimately boosts pigment production. In melanocytes, signals from UV-irradiated keratinocytes stabilize p53 and lead to the release of pro-opiomelanocortin, which is processed to α‑MSH. α‑MSH binds to MC1R on melanocytes, raising cAMP levels and activating PKA, which phosphorylates CREB. CREB activation promotes MITF, a transcription factor that drives the expression of melanogenic enzymes like tyrosinase. With more tyrosinase and related enzymes, melanin is synthesized in melanosomes and then transferred to keratinocytes, increasing pigmentation and protecting skin from UV damage. Ribosome synthesis would be a general increase in protein production, not specifically about melanin. Degradation of DNA isn’t a direct normal response for making pigment, and blocking protein synthesis would hinder pigment production.

UV exposure in skin cells sets off a signaling cascade that ultimately boosts pigment production. In melanocytes, signals from UV-irradiated keratinocytes stabilize p53 and lead to the release of pro-opiomelanocortin, which is processed to α‑MSH. α‑MSH binds to MC1R on melanocytes, raising cAMP levels and activating PKA, which phosphorylates CREB. CREB activation promotes MITF, a transcription factor that drives the expression of melanogenic enzymes like tyrosinase. With more tyrosinase and related enzymes, melanin is synthesized in melanosomes and then transferred to keratinocytes, increasing pigmentation and protecting skin from UV damage.

Ribosome synthesis would be a general increase in protein production, not specifically about melanin. Degradation of DNA isn’t a direct normal response for making pigment, and blocking protein synthesis would hinder pigment production.