Binds to intron-containing transcripts and is involved in quality control for the export of spliced mRNAs from the nucleus (PubMed:14769921, PubMed:24452287). Binds to pre-mRNAs until splicing is completed or until faulty mRNAs are degraded. On correctly spliced mRNAs, GBP2 and HRB1 recruit MEX67 to allow nuclear export. On faulty mRNAs, GBP2 and HRB1 associate with the TRAMP complex that guides those pre-mRNAs to the exosome for degradation (PubMed:24452287). Binds single-stranded telomeric sequences of the type (TG[1-3])n in vitro (PubMed:7800479). Influences the localization of RAP1 in the nuclei (PubMed:7777547). Involved in modulating telomere length (PubMed:12519786). Nuclear at steady state. Export is dependent on active transcription and the export of mRNAs in general. Depends on MFT1 and HPR1 for nuclear export (PubMed:14676199). Becomes predominantly cytosolic after exposure to hypoxia (PubMed:22932476). RRM 1 and RRM 2 recognize preferentially RNAs containing the core motif GGUG. The atypical C-terminal RRM domain (RRM 3) does not interact with RNA/DNA, but is crucial for interaction with the THO/TREX complex. Methylated by HMT1. Present with 2540 molecules/cell in log phase SD medium.