One tumor suppressor gene is described as the most studied of its kind and is mutated in over half of all cancer types. Which gene is this, and what is its normal molecular function?

1. Tumor suppressor genes are active in normal cells to prevent uncontrolled cell growth. 2. The most studied tumor suppressor gene is p53, which is mutated in over 50 percent of all cancer types. 3. The p53 protein itself functions as a transcription factor that can bind to promoter sites of target genes. 4. Mutation of p53 in cancer will dramatically alter the transcriptional activity of its target genes. 5. p53 is not described as a ribosomal subunit, so that option misstates its molecular role. 6. myc is instead an oncogene aberrantly activated in Burkett's lymphoma, and RAS is a G-protein in growth-factor signaling, so neither matches the description of the most studied tumor suppressor gene. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 16 "Gene Expression", section Tumor Suppressor Genes, Oncogenes, and Cancer_