9.21-9.25 Flashcards
what does hnRNP stand for
heterogeneous nuclear ribonucleoprotein particle
what are hnRNPs
complexes of pre-mRNA associated with proteins
function of hnRNPs
involved with RNA folding so it can be processed
are 5’cap and Poly-A tail proteins hnRNPs
no
only __________ and __________ processed mRNAs are exported usually
completely, correctly
ex. of mRNAs that are exported before processing
- Hac1p
- viral genomes (HIV)
HIV exporting RNA genome without intron removal
- HIV produces protein REV
- REV binds to RRE (REV response element) on unspliced HIV-1 mRNA
- REV has NES, exports out of nucleus
ex. of constitutive mRNA
- ribosomal protein
- cytoskeletal fiber protein
ex. of regulated mRNA
heat shock response and poly A+ RNAs
processing associated with transcription:
- 5’ 7-methylGuanosine cap (occurs while RNA pol II not much farther along
- splicing - during transcription
- Poly-A tail - occurs after 3’ end is generated by endonuclease (RNA pol hasn’t stopped yet)
what adds poly-A tail
Poly-A polymerase
after splicing, what proteins will be on mRNA?
- EJC (exon junctional complex) remains bound to exon/exon splice site
- EJC includes Aly - interacts with spliceosome and TAP
- TAP - binds to FG repeats and can have karyopherin activity
after proteins on mRNA, it is considered
mRNP (messenger ribonucleoprotein particle)
what is an exosome made up of
ribonucleases
exosome
complex of ribonucleases located near tcr sites that degrades mRNAs processed incorrectly
what is likely involved in the removal of mRNP proteins?
Dbp5 - essential mRNA export protein
DEAD-box proteins
hydrolyze ATP, function in mRNA metabolism
RNA of snRNP
U snRNA
what is U snRNA made by
RNA polymerase II
modification of U snRNA at first in nucleus
addition of 5’ 7-meGuanosine cap
what does 5’ 7-meGuanosine cap serve as in U snRNA
signal to cytoplasm
modification of U snRNA in cytoplasm
- methylated (x2) to make trimethyl-G cap
- associated with other proteins to form U snRNP complex
what brings U snRNP back into nucleus
- snurportin
- importin B
modification of U snRNP in nucleus
addition of more proteins in Cajal bodies and GEMS
what transcribes microRNAs
RNA polymerase II in nucleus
where are micorRNAs usually found
introns of protein-coding genes or intergenic regions
what are miRNAs important for
development, differentiation, apoptosis
where do miRNAs bind to target mRNA
cytoplasm
role of miRNA with mRNA
blocks tsl, can promote mRNA degradation
processing steps of miRNA
- precursor in nucleus processed by Drosha (Pasha)
- exported by exportin
- Dicer further processes to yield functional miRNA
