Organization of the human gene encoding heterogeneous nuclear ribonucleoprotein type I (hnRNP I) and characterization of hnRNP I related pseudogene.

The human gene hnRNPI encoding the heterogeneous nuclear ribonucleoprotein type I, an alternative splicing modulator of tissue-specific transcripts, also known as PTB (polypyrimidine tract-binding protein), was recently mapped on chromosome 14, as well as on chromosome 19, suggesting that two closely related copies of the same gene might exist in the human genome. We report here that the gene localized on chromosome 14 corresponds to a highly homologous processed pseudogene related to hnRNPI gene (psihnRNPI). Analysis by RT-PCR and by EST database comparison indicates that psihnRNPI is not expressed. In this report we have also analyzed the organization of the actual hnRNPI gene localized on chromosome 19. The DNA sequence at the intron-exon boundaries unveiled the possible mechanism by which three isoforms of the protein (namely hnRNPI, PTB2 and PTB3) are generated by means of alternative splicing of the same hnRNPI gene transcript.