Post-transcriptional regulatory networks are dependent on the interplay of many 
RNA-binding proteins having a major role in mRNA processing events in mammals. 
We have been interested in the concerted action of the two RNA-binding proteins 
hnRNP A1 and HuR, both stable components of immunoselected hnRNP complexes and 
having a major nuclear localization. Specifically, we present here the 
application of the RNA-immunoprecipitation (RIP)-Chip technology to identify a 
population of nuclear transcripts associated with hnRNP A1-RNPs as isolated from 
the nuclear extract of either HuR WT or HuR-depleted (KO) mouse embryonic 
fibroblast (MEF) cells. The outcome of this analysis was a list of target genes 
regulated via HuR for their association (either increased or reduced) with the 
nuclear hnRNP A1-RNP complexes. Real time PCR analysis was applied to validate a 
selected number of nuclear mRNA transcripts, as well as to identify pre-spliced 
transcripts (in addition to their mature mRNA counterpart) within the isolated 
nuclear hnRNP A1-RNPs. The differentially enriched mRNAs were found to belong to 
GO categories relevant to biological processes anticipated for hnRNP A1 and HuR 
(such as transport, transcription, translation, apoptosis and cell cycle) 
indicating their concerted function in mRNA metabolism.