Chapter 10: RNA Processing Flashcards
RNAs are synthesized from DNA templates that are not functional -> need to be modified to make mature, functional RNA
precursor RNAs (pre-RNAs)
alterations of pre-RNAs are known as ()
RNA processing
benefits of RNA processing: RNA processing provides:
- regulation of gene activity
- diversity
- quality control
tRNA and rRNA transcripts are made as () that must be processed
long precursors
an () precursor encodes 3 rRNAs and several tRNAs
E. coli
the () precursor encodes 3 rRNAs
S. cerevisiae
encoding several RNAs in one precursor ensures that ()
similar amounts of each RNA are made
() cleave RNAs into smaller parts
ribonucleases
successively remove nucleotides from the end of a transcript; most often in 3’ to 5’, but sometimes in 5’ to 3’
exonucleases
exonucleases are not usually (1), and generally act on (2)
- sequence-specific
- single-stranded ends
cleave the DNA within the strand; some are specific for double-stranded RNA, some for single-stranded
endonucleases
examples of endonucleases
RNase III and RNase P
excision of bacterial rRNAs from longer precursors is performed by (); as well as trimming if some RNAs and tRNAs
RNase III
RNase III binds () in the pre-RNAs and cleaves the dsRNAs
stem structures (dsRNA)
endonucleases similar to RNase III are involved in many processes, e.g. in eukaryotes, they generate (1) and (2) that inhibit the expression of detrimental genes
- microRNA (miRNA)
- small interfering RNAs (siRNAs)
5’ trimming of tRNAs is done by the endonuclease ()
ribonuclease P, RNase P
unlike RNase III, RNase P enzymes have (1) component and (2) components
- bacterial RNA
- protein
in RNase P, the bacterial RNA component alone can cut RNA, thus acting as a ()
ribozyme
the () RNase P RNA component cannot cut RNA alone, but is essential for function
eukaryotic, archaeal, and mitochondrial
() are present in some tRNAs and rRNAs
introns
tRNA splicing is catalyzed by ()
protein factors
some rRNAs introns can catalyze their own removal -> they are ()
self-splicing
the 3’ ends of mature tRNAs have a conserved () -> attachment site for the amino acid
CCA sequence
CCA sequence is mostly added by ()
polymerization without template