Blocks the binding of HNRNPA1 to the intronic sequences flanking exon 9 of the PKM gene by competitively binding to the HNRNPA1 RGG-box motif (PubMed:28985503). This inhibits inclusion of exon 9 and promotes inclusion of exon 10, suppressing formation of the PKM M2 isoform and promoting production of the M1 isoform (PubMed:28985503). Also suppresses HNRNPA1-mediated processing of microRNA 18a (miR-18a) (PubMed:28985503). Promotes MYC stability through interaction with IGF2BP2 (PubMed:34457052). {ECO:0000269|PubMed:28985503, ECO:0000269|PubMed:34457052}. This is the function of HOXB-AS3 (HOXB cluster antisense RNA 3, Ensembl gene identifier ENSG00000233101).