2020 L6 Protein Translation and Protein Structure

Protein Homeostasis

• Maintaining balanced proteome = cells coordinate functions of protein synthesis and folding, conformational maintenance and degradation

How do genes encode more than one mRNA transcript

• Alternative promoter selection

  • most genes contain more than one promoter

  • allows transcription to be driven from alternative versions of first exon

  • purpose not fully understood, could allow for tissue or specific gene expression

  • different isoforms with different properties e.g. CDKN2A

• Alternative splicing

  1. mRNA undergoes splicing before maturation

  2. intronic RNA segs are removed and discarded and remaining exonic segs are joined end-to-end

  3. Splicing done by spliceosome, a complex of small nuclear RNA (snRNA) and proteins

Alternative splicing

• Allows one primary transcript to encode multiple protein isoforms

• One or more exons may be skipped, or additional ones included, or vary in length by repositioning the exon-intron junction

• Isoforms may or may not be functional and many simply reflect im

oops