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In this article we will discuss about the maturation of mRNA from HnRNA.
In higher organisms, within the nucleus, heterogenous nuclear RNA (HnRNA) or high molecular weight RNA (HMW RNA) or DNA-like-RNA (dRNA) is synthesized. These molecules are larger than mRNA and used in cytoplasm. Polymerase-I is added at 3′-end of HnRNA.
Subsequently mRNA molecule is released when HnRNA having polymerase I sequence at 3′-end disintegrates at the 5′-end. The mRNA passes out of the nuclear membrane into the cytoplasm and there it participates in protein synthesis. Recent studies have shown that the 5′-end is marked by 7-methyl guanosine.
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Poly A at 3′-end is generally called ‘tail’ and the blocked methylated 5′ termini are usually called ‘caps’.
