Study of the Coupling Between Transcription and mRNA Processing Utilizing a Novel Bcl-x Mini-gene

The Bel family of genes are fundamental to the apoptotic mechanism. Bcl-x a
member of this family, is alternatively spliced to create two main isoforms a long
(Bcl-xL) and a short (Bcl-xS) variant. The long form exhibits anti-apoptotic activity,
while the short form favors apoptosis. The proper balance of expression of these two
isoforms is crucial for several developmental processes such as thymic selection and
neural reshaping. A number of cancer types have been shown to over-express the long
form, thereby granting them some protection from apoptosis. To study the
transcriptional and post-transcriptional mechanisms regulating gene expression, the
Bcl-x gene has been utilized. A complex mini-gene construct has been create in order
to monitor the effects that promoter sequences, 5'UTR and 3'UTR's have on mRNA
splicing, RNA export, stability and translation. Abundant evidence exists indicating
that RNA processing events such as transcription, splicing and export are coupled, yet
the mechanisms and factors involved in regulating these processes are poorly
understood. The mini-gene is identical to the endogenous gene with the exception of a deletion to the 50Kb intron and the addition of a tag to differentiate the mini-gene
product from the endogenous mRNA and protein. This novel system allows for the
study of transcriptional and post-transcriptional mechanisms regulating gene
expression from RNA biogenesis on to the protein level.