Select all mechanisms used by eukaryotic cells to inhibit initiation of translat

Question

Select all mechanisms used by eukaryotic cells to inhibit initiation of translation as a means to regulate translation.

Check all that apply.

Check all that apply.

- An RNA binding protein can bind near the ribosome-binding site (RBS) and block the 16S rRNA in the small subunit from binding. - Phosphorylation of the alpha subunit of eIF2B (a GTP-exchange factor for eIF2) inhibits its action, leading to reduced levels of eIF2–GTP. - The mRNA may base-pair with itself to block access to a RBS, translation of one ORF may disrupt this base pairing to allow translation of the inhibited ORF. - In their unphosphorylated state, 4E-BP proteins, which compete with eIF4G for binding to eIF4E, bind to eIF4E tightly.

Explanation / Answer

Answer:

Phosphorylation of the alpha subunit of eIF2B (a GTP-exchange factor for eIF2) inhibits its action, leading to reduced levels of eIF2–GTP.

In their unphosphorylated state, 4E-BP proteins, which compete with eIF4G for binding to eIF4E, bind to eIF4E tightly.

Reason:

Eukaryotic translation regulation:

Normally, after binding of correct codon and anti codon, the new amino acid is linked to the growing polypeptide chain in the P –site (peptidyl site) by a peptide bond. This process is catalyzed by an enzyme peptidyltransferase located at the peptidyl transferase center of the large ribosomal subunit (ribozyme, a multicomplex protein ribosome). A new peptidyl-tRNA now occupies the A site. The empty tRNA now moves to the E site and this process facilitated by another elongation factor (eEF 2) and GTP. The new peptidyl tRNA moves to the P site, and the cycle repeats until it reads a stop codon. The following picture depicts the various stages in elongation.

Phosphorylation of the alpha subunit of eIF2B (a GTP-exchange factor for eIF2) inhibits its action, leading to reduced levels of eIF2–GTP so that elongation of peptide chain inhibited. The unphosphorylated state, 4E-BP proteins, which compete with eIF4G for binding to eIF4E, bind to eIF4E tightly so that translation is stopped because of incorrect charging of each tRNA molecules is leading to" no binding of correct codon and anti codon". The new amino acid is not going to link the growing polypeptide chain in the P –site (peptidyl site) by a peptide bond

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