Gene Expression

The formation of mature mRNA from heterogeneous nuclear RNA (hnRNA) occurs through a process known as RNA processing.
The major steps involved in mRNA maturation are:
Capping:
(i) A 7-methylguanosine (m⁷G) cap is added to the 5’ end of the hnRNA.
(ii) This protects the mRNA from degradation and facilitates ribosome recognition.
Splicing:
(i) Non-coding regions (introns) are removed, and coding sequences (exons) are joined together.
(ii) Performed by a spliceosome complex.
Polyadenylation:
(i) A poly-A tail (about 200 adenine residues) is added at the 3’ end.
(ii) Helps in mRNA stability and transport.