In-vitro dual binding activity of a evolutionarily related subgroup of hnRNP proteins.

The wide family of heterogeneous nuclear ribonucleoproteins (hnRNPs) comprises members that interact with single-stranded nucleic acids. On the basis of their structure, some of them are characterised by a tandem RNA-binding domain (RBD) and a glycine-rich C-terminus, showing a high degree of homology. Recently, we have isolated some proteins belonging to this group that interact with single-stranded cytosine-block telomeric DNA. The aim of the present investigation is to better characterise the relationship of some structural features shared by these proteins and their in-vitro interaction with the telomeric type sequences. We analysed the in-vitro binding properties of some of these components toward both single-stranded telomeric motifs. Using deletion mutants, the relationship between cytosine-rich motif binding activity and the structural features of one of these proteins is further characterized. This binding activity appears to be related to a subgroup of the 2xRBD+Glycine rich hnRNP, suggesting functionally distinct properties of these proteins, in agreement with their evolutionary relationship.