Epigenetics of Reproduction in Animals - Building the Most Complex Structure on Earth - page 77

RNA transcript (pre-mRNA)

Exon Exon 1 Exon 2

Intron

Protein Protein

snRNA

1

Other proteins

snRNA

snRNPs

Spliceosome

2

5' 5'

Spliceosome
components com

Cut-out
intron

mRNA

3 5'

Exon 1 Exon 2

Figure 2.10 Diagram of removal of an intron from the pre-mRNA.
Source : From AP Chapter 17, “From Gene to Protein,” http://www.quia.com/jg/1269935list.
html .

( Oesterreich et al., 2011 ). They are roughly the size of ribosomes and are crucially
involved in the AS process. The spliceosome is activated upon binding a pre-mRNA
transcript. In this active form, it removes introns and joins the exons of the pre-
mRNA to build a protein ( Figure 2.10 ).

Epigenetic Determination of AS
Introns in the pre-mRNA have splice site sequences at both ends, but they are too
degenerate to sufficiently always recognize correct splice sites. There is evidence
that chromatin remodeling via histone acetylation/deacetylation helps in determin-
ing splice sites. A clear correlation is observed between the epigenetic marks (DNA