Lecture 28 - Transcription and RNA Processing Flashcards
what are 3 major cellular RNA functions?
- messenger RNAs (mRNA)
- transfer RNAs (tRNA)
- ribosomal RNAs (rRNA)
where are all RNAs transcribed from?
DNA templates by RNA polymerases (RNAP)
where are RNAs synthesized in eukaryotes?
cell nucleus
where are RNAs synthesized in prokaryotes?
cytosol
what are the 3 stages of transcription?
- initiation
- termination
- termination
what is a barrier to transcription?
the packaging of eukaryotic DNA into chromatin
where is transcription regulated?
in all cells
what do sigma factors do?
direct bacterial RNA polymerase to promoters
where do sigma factors bind?
to specific sequences that define bacterial promoters
can sigma factor activity be regulated?
yes, in many ways
what is the sigma unit of the RNA polymerase?
the specificity filter
how does the sigma subunit work?
different sigma associate with the other subunits in the polymerase to search for the preferred promoter sequence
in promoter binding what happens once the promoter region has been recognized?
sigma unbinds + core polymerase stays bound + processive
what does eukaryotic RNA polymerases require?
general transcription factors for promoter recognition
what are eukaryotic promoters often defined by?
TATA box + other core promoter elements
how does transcription proceed?
highly processive manner
what are elongation factors?
- they suppress the pausing of transcription
- rescue stalled polymerase enzymes
what must happen to nucleosomes during elongation?
nucleosomes must be removed from the path of elongating polymerase for transcription to proceed
what are 2 types of termination in prokaryotic transcription?
- Rho-independent
2. Rho-dependent
what happens in Rho-independent termination?
- G:C pairs form stable stem-loop structure
- terminator causes transcript to unbind from the bubble
rho works like a _____
helicase
how are prokaryotic genes organized?
into operons
in bacteria cells, several ____ are often expressed ____
protein-coding genes
together
what are operons?
protein-coding genes that are often expressed together
