Question

Pretranscriptional, Transcriptional, RNA Processing, RNA Transport,Translational, and posttranslational.

Choose 1 of the above levels of gene regulation in Eukaryotes and explain how it functions in gene regulation of eukaryotic gene expression.

Answer 1

TRANSLATIONAL-LEVEL GENE REGULATION IN EUKARYOTES

Protein synthesis or translation is mainly regulated at the initiation stage. This results in the rapid control of gene expression.

For eukaryotic translation to begin, the ribosome should assemble on the mRNA. This process is accompanied by the help of several proteins known as 'helper proteins'. One of such protein involved in the initiation of translation is eukaryotic translation Initiation factor 2 (eIF-2). Translation can be initiated only when this protein binds to the smaller subunit of the ribosome. So translation can be regulated by making this protein active or inactive. In a non- phosphorylated condition eIF-2 is said to be 'on' or active and it can carry out its function. But when eIF-2 is phosphorylated, it is turned 'off'. Which means it undergoes some conformational changes due to the addition of the phosphate group and it can no longer play its role in initiation of translation- This is one way of regulation of eukaryotic translation.

Translational level gene regulation occurs during the elongation step of the translation as well. The newly synthesizing polypeptide chain is transported from the A-site of the ribosome to the p-site with the help of a protein known as eukaryotic elongation factor 2 (eEF2). Only non-phosphorylated eEF2 can bind to the ribosome to perform its function. When it is phosphorylated at the amino acid threonine (56th position), eEF2 becomes unable to bind to the ribosome and carry out its function. So translation process becomes halted. This is one way of regulating eukaryotic translation at the elongation level.