Regulation of Gene Expression

Question 1

Transcriptional Control

Answer 1

Control access of RNA polymerase to gene and controlling efficiency of transcription

Controls if mRNA made and if so how much is made

More DNA methylation= less chromatin accessibility

Question 2

Post-Transcriptional Control

Answer 2

Control at level of RNA processing (alt splicing or polyadenylation), mRNA transport, mRNA stability translation of mRNA by ribosomes

If fixed amount of mRNA… how can given mRNA be modified to achieve different expression (how much protein and what types of proteins are made)

Question 3

2 Classes of Elements in Transcriptional Control

Answer 3

1- cis acting elements
(DNA sequence elements adjacent to or w/in gene)

2- activator or repressor proteins
(bind DNA and/or interact w/ transcription proteins)

Question 4

Cis-acting elements

Answer 4

Can have mult diff activators/proteins that bind to them –> diff isoforms of same protein

Question 5

How do we obtain variety in proteins formed?

Answer 5

A gene can contain more than 1 promotor and a promotor can be bound by multi activators or repressors

Question 6

Regulation by Phosphorylation

Answer 6

Involves kinases that add phosphates to structures (adding phosphate can either activate or tag for destruction)

This is transcriptional control

Question 7

Regulation by Alt Promotor Use

Answer 7

Alt promotors –> tissue-specific isoforms or protein

This is transcriptional control

Question 8

Alternative Polyadenylation

Answer 8

Polyadenylation can keep introns from being spliced –> alt form of protein made

This is post-transcriptional control

Question 9

Alternate Splicing

Answer 9

Primary transcript can be spliced diff ways —> distinct mRNAs —> various proteins

This is post-transcriptional control

Question 10

RNA editing

Answer 10

rare; single nucleotide is substituted in RNA

This is post-transcriptional control

Question 11

RNA Interference (RNAi)

Answer 11

RNAi is important cellular process involved in regulation of gene expression at a post transcriptional level; utilizes antisense RNAs that vary greatly in size and include moderate to large-sized antisense RNAs as well as miRNAs

Question 12

MicroRNAs (miRNAs)

Answer 12

• very small and can regulate gene expression by an antisense mechanism
• miRNAs are coded by noncoding sequences of genome AND introns of protein coding genes
• Attachment of miRNA will either degrade the mRNA or inhibit translation depending on the degree of mismatch b/n miRNA and mRNA (BIND TO UTR)
  
  • Perfectly paired … degraded
  • Imperfectly paired…inhibit translation

1 mRNA can be regulated by MULT miRNAs…single miRNA can regulate MULT mRNAs