Three isoforms of RARB exists in human and four exists in mouse. RARB1, B2, B3 and B4 are generated by two promoters and alternative splicing. RARB1 and RARB3, the isoform only detected in mouse, are transcribed from the same promoter and differ only in their N-terminal part.^[1][2] RARB2 and RARB4 are generated by a downstream promoter that contains a retinoic acid response element.^[1][3][4] RARB4 is initiated from a CUG codon and differ from RARB2 by its N-terminal part.^[2]

The transcriptional activity of RARB is modulated by modifications such as phosphorylation, ubiquitination, sumoylation and methylation. These post-translational modifications influence the cellular localization of the receptor, its heterodimerization with RXRs, DNA binding and its degradation.^[1]

RA induces RAR phosphorylation on serine residues in the ligand binding domain and in the N-terminal region. In addition, kinases activated by other signaling pathways can also phosphorylate RARs at other sites. For instance, PKC-mediated phosphorylation of RARs in the DBD results in abrogation of DNA binding and/or nuclear export.^[1]