An assortment of rna molecules assembled around newly transcribed rna (pre- messenger rna, or pre-mrna) in the cell nucleus. The hnrna associates with proteins to form heterogeneous nuclear ribonucleoprotein (hnrnp). After release from the chromosome and processing of the pre-mrna by the spliceosome (see intron), the mature messenger rna remains associated with various proteins, forming a messenger ribonucleoprotein (mrnp), which is then exported from the nucleus hnrnp: Heterogeneous nuclear ribonucleoproteins (hnrnps) are complexes of rna and protein present in the cell nucleus during gene transcription and subsequent post- transcriptional modification of the newly synthesized rna (pre-mrna). The presence of the proteins bound to a pre-mrna molecule serves as a signal that the pre-mrna is not yet fully processed and ready for export to the cytoplasm. After splicing has occurred, the proteins remain bound to spliced introns and target them for degradation. snrna: Short rnas, and forms complexes with proteins in snrnps. snrnas are involved in.