Chapter 16 Flashcards
The immediate RNA product of transcription before any posttranscriptional processing reactions.
Primary Transcript
A sequence of nucleotides in a gene that is transcribed but excised before the gene is translated. Also called an intervening sequence.
intron
The segment of a eukaryotic gene that encodes a portion of the final product of the gene; a segment of RNA that remains after posttranscriptional processing and is transcribed into a protein or incorporated into the structure of an RNA.
exon
A residue of 7-methylguanosine (7-meG) linked to the 5′-terminal residue of an mRNA through a 5′,5′-triphosphate linkage, which protects the mRNA from exoribonucleases.
5’ Cap
A protein complex that recruits capped mRNAs to the ribosome to initiate translation.
cap-binding complex
A length of adenosine residues (typically 80 to 250) added to the 3′ end of many mRNAs in eukaryotes (and sometimes in bacteria), which serves as a binding site for proteins that protect the mRNA from exonucleases.
3′ poly(A) tail
The site where an mRNA is cleaved by a specific endonuclease to generate the free 3′ hydroxyl to which A residues are added. The site is marked by a highly conserved 5′-AAUAAA sequence 10 to 30 nucleotides on the 5′ side, and a G- and U-rich region 20 to 40 nucleotides on the 3′ side.
poly(A) addition site:
The removal of introns and joining of exons in a primary transcript
RNA splicing
A ribonucleoprotein complex that splices mRNAs in eukaryotic cells
spliceosome
The splicing of exons from a single gene in various combinations to produce different mRNAs and thus different polypeptides.
alternative splicing
The existence of more than one site in an mRNA that may be cleaved to generate the free 3′ hydroxyl to which A residues are added, which can generate diverse transcripts from a single gene.
poly(A) site choice
An internal A residue just upstream of the 3′ splice site of an intron that attacks the phosphate at the 5′ splice site, forming the loop of the intron lariat.
branch point
A protein and snRNA complex, found in the nucleus and a component of the spliceosome.
small nuclear ribonucleoprotein (snRNP):
A class of short, noncoding RNAs, typically 100 to 200 nucleotides long, found in the nucleus and involved in the splicing of eukaryotic mRNAs.
small nuclear RNA (snRNA):
A large, self-splicing ribozyme that catalyzes its own excision from an mRNA, tRNA, or rRNA transcript in a reaction that requires a guanosine nucleotide or nucleoside to initiate the reaction.
Group 1 Intron
A large, self-splicing ribozyme that catalyzes its own excision from an mRNA transcript as a lariat structure.
Group 2 Intron
A process in nematode worms in which a short leader sequence is spliced to the 5′ end of a primary transcript from a separate RNA molecule.
trans-splicing
The posttranscriptional modification of an mRNA that alters one or more codons prior to translation.
RNA editing
The enzymatic removal of amino groups from biomolecules such as amino acids or nucleotides.
deamination
A protein complex that catalyzes the insertion or deletion of nucleotide residues during the process of RNA editing
editosome
An enzyme that catalyzes the conversion of adenosine to inosine by removal of the amino group at C-6 on the adenine ring.
adenosine deaminase acting on RNA (ADAR):
A family of nuclear transport receptors including importins and exportins
karyopherins
A protein receptor responsible for transporting noncoding RNAs processed in the cytoplasm into the nucleus through a nuclear pore.
importin
A protein receptor responsible for transporting RNAs from the nucleus, through a nuclear pore, into the cytoplasm.
exportin
A molecular complex of RNA and protein, such as the ribosome.
ribonucleoprotein (RNP):
A complex of proteins deposited on an mRNA by the spliceosome 20 to 24 nucleotides upstream of exon-exon junctions.
exon junction complex (EJC)
The complete hydrolysis of RNA into its component ribonucleotides, usually catalyzed by ribonucleases or the exosome
RNA degradation
A complex of 3′→5′ exonucleases in eukaryotic cells that processes the 3′ ends of rRNAs and tRNAs and is responsible for RNA degradation in higher eukaryotes.
exosome
A pathway for degradation of mRNA molecules with a premature stop codon, triggered by the presence of an exon junction complex on a transcript that has been translated.
nonsense-mediated mRNA decay (NMD):
An area in the cytoplasm of a eukaryotic cell where mRNAs that are not being translated are sequestered, possibly for degradation.
processing body (P body)
The primary transcript of ribosomal RNAs in bacterial and eukaryotic cells, which is processed into mature ribosomal RNAs (and transfer RNAs in bacteria).
preribosomal RNA (pre-rRNA):
A protein and snoRNA complex that guides the modification of rRNAs in the nucleolus
small nucleolar ribonucleoprotein (snoRNP):
A class of short, noncoding RNAs, generally 60 to 300 nucleotides long, found in the nucleolus and involved in the modification of rRNAs.
small nucleolar RNA (snoRNA):
A class of small RNA molecules (21 to 23 nucleotides after processing is complete) involved in gene silencing by inhibiting translation and/or promoting the degradation of particular mRNAs.
microRNA (miRNA)
An endonuclease in eukaryotic cells that cleaves the hairpin of primary miRNA transcripts to produce pre-miRNAs.
Drosha
An endonuclease in eukaryotic cells that catalyzes the hydrolysis of double-stranded RNAs, producing siRNAs or processing pre-miRNAs to mature miRNAs. Dicer also plays a role in the creation of RNA-induced silencing complexes.
Dicer:
