Question

Lab Activity for RNA Processing: p53 Isoforms Isoforms, simply defined, are different proteins created from the same genomic sequence. These differences can be created by a variety of mechanisms, including alternative splicing, the usage of different promoters, and the usage of different start codons. The p53 gene (usually called Tp53) is located on the short arm of chromosome 17 in the human genome. It has some unique gene topography, including one non-coding exon and very long intron spanning almost 10,000 base pairs. There are five exons that show a high degree of conservation across all vertebrates, and orthologs for p53 have been found in most other genomes that have been sequenced. Below is an image of the full-length p53 protein and the specific functions of different regions of the protein. The numbers on this particular diagram indicate amino acids, not nucleotides. N-domain core domain C-domain 292 300 323 324 355 1 42 63 97 98 363 393 proline-rich domain NLS NES basic domain transactivation domain DNA-binding domain tetramerization domain In humans, there are at least 12 human p53 isoforms that have been identified formed by a variety of mechanisms. For this activity, use primary research sources you can find online or other resources to: 1) Identify the 12 human p53 isoforms (they have names that indicate which regions are different) 2) Identify how the mechanism by which each of these isoforms is created. 3) Using the diagram above, identify which functional regions of the protein are altered in these different isoforms.
three part question!!!!

Answer 1

answers:

a) the human p53 gene expresses not only 1 but 12 different p53 isoforms (proteins) which is due to the alternative initiation of translation, alternate splicing, alternative promotor usage. they are expressed in normal human tissues expression but they are abnormally expressed in a wide range of cancer type.

1. p63 : expresses at least three alternating spliced c-terminal isoforms
2. p73 :expresses at least seven alternating spliced c-terminal isoforms

they both share a significant structural and functional similarity with the p53. +

• p53 , p53$\beta$ ,p53$\gamma$ $\Delta$ 40p53$\alpha$  $\Delta$40p53$\beta$
• $\Delta$40p53$\gamma$  $\Delta$133p53$\alpha$
• $\Delta$133p53$\beta$ $\Delta$ 133p53$\gamma$
• $\Delta$160p53$\alpha$ $\Delta$ 160p53$\beta$ $\Delta$ 160p53$\gamma$

ans 2): mechanism by which each of these are made:

• $\Delta$133p53$\alpha$, $\Delta$ 133p53$\beta$and $\Delta$ 133p53$\gamma$: transcription of p53 mRNA from the internal promoter (intron 4) directed to alternative splicing of exon 9b.
• $\Delta$160p53$\alpha$, $\Delta$ 160p53$\beta$ and $\Delta$ 160p53$\gamma$ : encoded by $\Delta$ 133p53$\alpha$, $\Delta$ 133p53$\beta$and $\Delta$ 133p53$\gamma$mRNAs by the alternative initiation of translation at ATG 160, which lies within a sequence environment matching Kozack's consensus criteria.
• p53$\beta$ : alternative splicing of intron 9 (exon 9b)
• p53$\gamma$: truncation of p53 protein of the last 60 amino acids and containing additional 15 amino acids.
• $\Delta$40p53$\alpha$, $\Delta$ 40p53 $\beta$ and $\Delta$ 40p53 $\gamma$ : obtained by classic splicing of the C-terminus and alternatively spliced c-terminal isoforms.

ans 3)

proteins which are translated from alternatively spliced mRNAs will have difference in their amino acids sequences therefore they will have difference in their functional properties.