Regulator of pre-B-cell leukemia transcription factors (BPXs) function. Inhibits the binding of PBX1-HOX complex to DNA and blocks the transcriptional activity of E2A-PBX1. Tethers estrogen receptor- alpha (ESR1) to microtubules and allows them to influence estrogen receptors-alpha signaling. {ECO:0000269|PubMed:10825160, ECO:0000269|PubMed:12360403, ECO:0000269|PubMed:17043237}. This is the function of ENSG00000163346 (PBXIP1, PBX homeobox interacting protein 1).