Cloning and functional analysis of human p51, which structurally and functionally resembles p53

Area of Science:

• Molecular Biology
• Cancer Genetics

Background:

• The p53 tumor suppressor gene is crucial in preventing human carcinogenesis by inducing cell cycle arrest or apoptosis in response to DNA damage.
• Identifying genes with similar functions to p53 is essential for understanding cancer development and exploring new therapeutic targets.

Purpose of the Study:

• To identify and characterize novel genes related to the p53 tumor suppressor.
• To investigate the functional roles of the newly identified p51 gene and its variants in cellular processes and cancer.

Main Methods:

• Degenerate polymerase chain reaction (PCR) was employed to search for p53-related genes.
• Cloning and characterization of splicing variants (p51A and p51B) of the novel p51 gene.
• Analysis of p51 mRNA expression patterns in various human tissues.
• Functional studies in p53-deficient cells to assess p51A's impact on growth suppression, apoptosis, and p21waf-1 upregulation.

Main Results:

• Two cDNA fragments distinct from p53 were identified, including the previously known p73 and a novel gene, p51.
• Two major splicing variants, p51A and p51B, were cloned, encoding proteins of different sizes.
• p51 mRNA exhibited restricted expression in specific tissues, unlike the ubiquitous p53 expression.
• In p53-deficient cells, p51A demonstrated growth-suppressive and apoptotic effects, upregulating p21waf-1.
• Mutations in the p51 gene were detected in some human epidermal tumors.

Conclusions:

• The p51 gene represents a novel family of p53-related genes with distinct expression patterns and functional roles.
• p51A exhibits tumor-suppressive activities, including growth inhibition and apoptosis induction, potentially through p53-dependent pathways.
• The presence of p51 mutations in epidermal tumors suggests its involvement in human carcinogenesis.