Gene promoters and gene regulation in eukaryotes Flashcards
what do the graph results mean?
peak at +50bp and then pauses
describe the graph results
transcription peaks at ~+50
RNA pol II initiates transcription and then pauses
what do CpG islands do?
occupy 70% of the promoter in genes transcribed at a low rate
contain less nucleosomes, easier to transcribe
TRANSCRIPTION INITIATES AT ANY POSITION WITHIN THE ISLAND –> not defined
transcription initiates in both directions, but proceeds in the direction of the open reading frame only
describe the transcription of sense and antisense transcripts
sense pauses before elongating further
antisense pause at other end of island and do not continue
describe the formation of the preinitiation complex
process starts with the association of TFIID to the promoter, followed by TFIIB and TFIIA
RNA pol is recruited. non-phosphorlyated CTD of RNA pol II establishes contact with GTCs
TFIIE and TFIIH are recruited
TFIIH helicase activity facilitates the opening of double helix DNA –> OPEN PIC
RNA pol initiates transcription
TFIIH kinase phosphorylates CTD to release RNA pol from promoter
describe the transition to elongation
after phosphorylation of CTD by TFIIH kinase, negative elongation factors, NELF and DSIF associate with RNA polymerase II and pause it downstream
another kinase, CDK9/CycT phosphorylstes the CTD and NELF
RNA pol II with a phosphorylated CTD is released
positive elongation factors PAF and Spt16 join the polymerase
DISF becomes a positive elongation factor
describe transcription elongation, AIDS, and HIV
5’ end of the short RNA is synthesized before polymerase pauses
short RNA forms a secondary structure called TAR
TAR holds polymerase and has an inhibitory effect of Cdk9/CycT
HIV1 encodes for protein Tat
Tat binds to TAR
upon cell stress other factors release polymerase and some Tat is made
when bound to TAR, Tat activates CDK9 kinase and releases the paused RNA pol II
more Tat is made and viral genes are fully exposed
describe HIV latency
dormant but activates upon stress when organism is weak, slowly killing T-cells and abolishing immunity
