[Molecular evolution and a speculative carcinogenesis mechanism for ras p21]

Area of Science:

• Molecular Biology
• Evolutionary Biology
• Genetics

Context:

• Ras p21 proteins are crucial signaling molecules found across diverse species, including humans, fruit flies, yeast, and viruses.
• Understanding the evolutionary dynamics of ras p21 is key to deciphering its role in normal cellular functions and disease.

Purpose:

• To analyze and compare amino acid sequences of ras p21 from various organisms.
• To estimate evolutionary rates (gene duplication and amino acid replacement) for ras p21.
• To investigate the evolutionary origins of viral ras genes and their relationship to cellular ras genes.

Summary:

• Analysis of ten ras p21 amino acid sequences revealed a mean concerted evolution duplication rate of 2.78 x 10(-9) per gene per year and a mean amino acid replacement rate of 2.23 x 10(-10) per year.
• The study traced the origins of viral ras genes (v-Has, v-Kis) to cellular counterparts (c-H-ras1, c-K-ras2) and indicated a common ancestor for human cellular ras genes (c-H-ras1, c-K-ras2, c-N-ras).
• Findings align with existing experimental data and propose a speculative model for carcinogenesis involving covarions and invarions, suggesting mutations at codons 12 or 61 in p21 may be critical for cancer progression.

Impact:

• Provides quantitative estimates for ras p21 evolutionary rates, contributing to molecular evolution studies.
• Elucidates the evolutionary relationships between viral and cellular ras genes.
• Offers a novel hypothesis on the role of specific ras p21 mutations in carcinogenesis, potentially guiding future cancer research.