The hnRNP 2H9 gene, which is involved in the splicing reaction, is a multiply spliced gene

The hnRNP 2H9 gene products are involved in the splicing process and participate in early heat shock-induced splicing arrest. By combining low/high stringency hybridisation, database search, Northern and Western blotting it is shown that the gene is alternatively spliced into at least six transcripts: hnRNPs 2H9, 2H9A, 2H9B, 2H9C, 2H9D and 2H9E predicting proteins containing 346, 331, 297, 215, 145 and 139 amino acids, respectively. The hnRNP 2H9A cDNA sequence was used to obtain a genomic BAC clone and the structure of the hnRNP 2H9 gene was revealed by sequencing two subclones together spanning about 6.7 kb. The six transcripts are processed from at least 10, 10, 8, 7, 5 and 4 exons, respectively, with all intron/exon junctions obeying the 'GT-AG' rule. The hnRNP 2H9 and 2H9A proteins contain two RNA recognition motifs of the quasi-RRM type found in the two C-terminal qRRMs of the hnRNPs H, H' and F proteins. The hnRNP 2H9B protein has a partially deleted N-terminal qRRM, which is completely deleted in hnRNP 2H9C. hnRNPs 2H9D and 2H9E contain only one slightly modified C-terminal qRRM. Furthermore, the six proteins vary in their auxiliary domains outside the qRRMs. Western blotting indicates that the alternatively spliced transcripts give rise to different sets and levels of proteins expressed among various human cells and tissues. Due to their great structural variations the different proteins may thus possess different functions in the splicing reaction.