Alternative splicing allows a pre-mRNA to be spliced in multiple ways, generating different proteins in different tissues or at different times in development (see Chapter 14). Many eukaryotic genes undergo alternative splicing, and the regulation of splicing is probably an important means of controlling gene expression in eukaryotic cells.
The T-antigen gene of the mammalian virus SV40 serves as a well-studied example of alternative splicing. This gene is capable of encoding two different proteins, the large T and small t antigens. Which of the two proteins is produced depends on which of two alternative 5' splice sites is used during RNA splicing (< Figure 16.25). The use of one 5' splice site produces mRNA that encodes the large T
ffi Use of the first 5' splice site produces an mRNA that encodes the large T antigen.
Alternative 5' splice sites .
^ Use of the second 5' splice site produces an mRNA that encodes the small t antigen.
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