Influence of bcl-x alternative promoter usage on its splicing pattern

HOIJMAN, E.; KORNBLIHTT, A.R.; PECCI, A

Pinamar, Argentina

Congreso; 41° congreso de SAIB y Congress of the Panamerican Association for Biochemistry and Molecular Biology; 2005

SAIB

Differential splicing from the bcl-X gene generates several isoforms with opposite effects on the apoptotic response (i.e. bcl-XL and Bcl-XS). We have demonstrated that the the 5’ upstream region of the mouse bcl-X gene contains five different promoters and presented evidences suggesting that promoter selection influences the outcome of the splice process. To test this hypothesis we constructed minigenes containing each promoter region upstream a common sequence with both 5´ alternative splice sites and an unique 3´splice site. We confirmed the minigenes activities by transient transfection in three different cell types (HC11, Hela and HEK). In all cases, we observed a more abundant expression of bcl-XL, however the ratio bcl-XL/bcl-XS was higher in cells transfected with the minigene that is under the control of promoter 3 (three times higher than minigenes from promoter 1), suggesting that promoter sequence could influence splice site selection. Co-transfections of constitutive STAT5A and B transcription factors (known as repressors of  promoter 1 activity) together with the minigene containing the promoter 1 raised 4±1 times the ratio of bcl-XL/bcl-XS suggesting a splicing effect of these transcriptional factors. Taken together these results suggest a coupling between a the regulation of transcription and splicing on bcl-X gene.