HMG-I/Y bind preferentially to the minor groove of A+T rich regions in double-stranded DNA. It is suggested that these proteins could function in nucleosome phasing and in the 3'-end processing of mRNA transcripts. They are also involved in the transcription regulation of genes containing, or in close proximity to A+T-rich regions. Interacts with HIPK2. Isoforms HMG-I and HMG-Y can be phosphorylated by HIPK2. Phosphorylation may modulate DNA-binding affinity (By similarity). Methylation at Arg-58 is mutually exclusive with methylation at Arg-60. Belongs to the HMGA family.