Chp1 Lec 10

Question 1

Discuss mechanisms of regulation that act at the level of transcription.

Answer 1

1. Antisense RNA
   - forms a double helix with mRNA and block translation
   - an artificial gene in the ‘ Flavr Savr’ tomato is transcribed to an antisense RNA that greatly reduces translation of a gene involved in ethylene synthesis, delaying ripening.
2. RNA interference
   - similar to antisense RNA and CRISPR/Cas
   - a short stretch of double stranded RNA (~20bp) elicits degradation by a ribonucleoprotein complex, of mRNA complementary to either of the RNA strands
   - gene knockouts in studies aimed at deducing gene functions
3. Attachment of ligands to the Shine-Dalgorno sequence in mRNA
   - prevents the mRNA (RBS) from binding to the ribosome
   - in E.coli, vitamins B1 an B12 bind to mRNA transcripts of genes involved in their biosynthesis- unique RNA- level feedback inhibition

Question 2

Discuss mechanisms of regulation that act at the level of translation of splice variants.

Answer 2

1. Degradation of specific mRNA variants by miRNAs and siRNAs - which may repress translation of specific splice variants.
2. Splicing factors ( thus, RNA - binding proteins) may interact with transcripts of specific exons ( or even introns) and splicing machinery to direct maturation of the mRNA.
3. At transcriptional level, chromatin remodeling may render certain exons inaccessible and affect expressed splice variant

Question 3

Briefly discuss some regulatory mechanisms that affect protein activity.

Answer 3

• modulating protein activity by post-translational modifications, some of which are reversible.
• e.g.ligand binding- inhibition and allosteric changes (lac operon)

Question 4

Overall regulatory processes are biochemically ___, but applied in coordinated ways. Also, chemical modifications of ___ can regulate amount of proteins in cells ___ vs on/off.

Answer 4

Distinct, TFs, quantitatively