Functional diversity of hnRNP proteins.

The hnRNP proteins bind to pre-mRNA concomitant with transcription and form ribonucleoprotein complex essential for post-transcriptional events. More than 20 different groups of hnRNP proteins are known in humans. The number seems to be similar in other organisms too. The hnRNP proteins possess different types of RNA binding domains which directly interact with RNA, most likely in a sequence specific manner. The functions of hnRNP proteins range from mRNA packaging and transport, to mRNA splicing and silencing. Further, indirectly, their role has also been implicated in oogenesis. Hence, hnRNP proteins play diversified roles both in nucleus and cytoplasm, and regulate the gene expression at various levels.