Alternative pre-mRNA processing regulates cell-type specific expression of the IL4l1 and NUP62 genes.
BACKGROUND
Given the complexity of higher organisms, the number of genes encoded by their genomes is surprisingly small. Tissue specific regulation of expression and splicing are major factors enhancing the number of the encoded products. Commonly these mechanisms are intragenic and affect only one gene.


RESULTS
Here we provide evidence that the IL4I1 gene is specifically transcribed from the apparent promoter of the upstream NUP62 gene, and that the first two exons of NUP62 are also contained in the novel IL4I1_2 variant. While expression of IL4I1 driven from its previously described promoter is found mostly in B cells, the expression driven by the NUP62 promoter is restricted to cells in testis (Sertoli cells) and in the brain (e.g., Purkinje cells). Since NUP62 is itself ubiquitously expressed, the IL4I1_2 variant likely derives from cell type specific alternative pre-mRNA processing.


CONCLUSIONS
Comparative genomics suggest that the promoter upstream of the NUP62 gene originally belonged to the IL4I1 gene and was later acquired by NUP62 via insertion of a retroposon. Since both genes are apparently essential, the promoter had to serve two genes afterwards. Expression of the IL4I1 gene from the "NUP62" promoter and the tissue specific involvement of the pre-mRNA processing machinery to regulate expression of two unrelated proteins indicate a novel mechanism of gene regulation.
Wiemann
Stefan
S
Molecular Genome Analysis, German Cancer Research Center, Im Neuenheimer Feld 580, Heidelberg, 69120, Germany. s.wiemann@dkfz.de
Kolb-Kokocinski
Anja
A
Poustka
Annemarie
A
D017398:Alternative Splicing; D000818:Animals; D005420:Flavoproteins / Q000235:genetics*; D005786:Gene Expression Regulation; D006801:Humans; D050830:L-Amino Acid Oxidase; D051379:Mice; D028861:Nuclear Pore Complex Proteins / Q000235:genetics*; D012322:RNA Precursors / Q000235:genetics*
D005420:Flavoproteins; C510282:NUP62 protein, mouse; D028861:Nuclear Pore Complex Proteins; D012322:RNA Precursors; C105158:IL4I1 protein, human; C484538:Il4i1 protein, mouse; D050830:L-Amino Acid Oxidase