Translation

Question 1

eIFs= euk initiation factors
eEFs = euk elongation factors

Answer 1

ya

Question 2

wat are the methods of proofreading which are used during translation?

Answer 2

• -nonsensed mediated decay
• -nonsense assoicated alt splicing
• -non-stop mediated decay

Question 3

Nonsense mediated decay

Answer 3

almost all genes contain the stop codon within the last exon of the mRNA; splicing leaves behind downstream commitment factors (DCFs) at exon-exon boundaries; if a stop codon is produced upstream of a DFC (as in, not the last exon) the mRNA is rapidly degraded by translational proofreading

Question 4

how are bad mRNAs degraded during nonsense mediated decay?

Answer 4

DCFs 3’ to the ribo activate Up-Frameshift proteins UPFs–>which activate decapping enzymes to remove the 5’ methyl guanine cap–>therefore, mRNA is rapidly degraded

Question 5

what is UPF used for?

Answer 5

activates decapping protein to remove the 5’ methyl guanine gap so mRNA is rapidly degraded

Question 6

waht is beta thalassemia

Answer 6

mutation of the beta globin of hemoglobin–>leads to decrease beta production (still tolerable in heterzyg state); homozygs have severe anemia

Question 7

how does NMD tie into beta thal?

Answer 7

protects individuals; NMD recognizes the incorrect splicing–>degrades mRNA–>no poisonous Beta Hb HOWEVER, if there is stop codon in the exon after the DCF, makes a toxic protein–NMD incompetent

Question 8

how does NAS work?

Answer 8

used a premature stop codon as well–more confusing; “minor” spliceosome involved (in cyto);

Question 9

how does NSMD work?

Answer 9

no stop codons–ORF just continues into polyA tail; ribosome can’t detach as it needs stop codon to recruit RRFs; Ski7 released the dead-end ribosome and recruits the exosome;

Question 10

what is the exosome?

Answer 10

3’-5’ exonuclease to degrade mRNA; polyA tail causes protien to have 10-100 lysine amino acids at the C terminus; lysines are recognized by the proteaseome and destroy the protein