Species-specific and isoform-specific RNA binding of human and mouse fragile X mental retardation proteins.
The loss of the fragile X RNA binding protein, FMRP, causes macroorchidism and mental retardation in man. The discovery of a mouse ortholog led to the development of several FMRP knockout mouse strains that recapitulate some features of the disease. As mouse and human FMRPs differ in several amino acids in their RNA binding domains, we compared the RNA binding profiles of these two orthologs. Five variant FMRPs, whose differences arose from alternative splicing and mutation within the conserved RNA binding domains, were examined. Homoribopolymer binding studies showed that human FMRPs (hFMRP) bound a broader range of single-stranded mimetics than mouse FMRPs (mFMRP) and these interactions were both complex and cooperative. hFMRP and mFMRP also displayed significant preferences toward binding their own mRNA; specifically we found that the mFMRP isoforms bind mFMR1 mRNA much more tightly than their human counterparts. Finally, these data demonstrate that each FMRP variant binds RNAs uniquely, resulting in a set of proteins with differing affinities.
Denman
Robert B
RB
Laboratory of Molecular Neurobiology, Department of Molecular Biology, New York State Institute for Basic Research in Developmental Disabilities, 1050 Forest Hill Road, Staten Island, New York 10314, USA. rbdenman@yahoo.com
Sung
Ying Ju
YJ
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects / Q000235:genetics; D002474:Cell-Free System; D051860:Fragile X Messenger Ribonucleoprotein 1; D005600:Fragile X Syndrome / Q000235:genetics; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D011061:Poly A / Q000737:chemistry / Q000378:metabolism; D011066:Poly C / Q000737:chemistry / Q000378:metabolism; D011068:Poly G / Q000737:chemistry / Q000378:metabolism; D011072:Poly U / Q000737:chemistry / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012313:RNA / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology; D013045:Species Specificity
D051860:Fragile X Messenger Ribonucleoprotein 1; D009419:Nerve Tissue Proteins; D011061:Poly A; D011066:Poly C; D011068:Poly G; D011072:Poly U; D020033:Protein Isoforms; D012313:RNA; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D012965:Sodium Chloride; C497683:FMR1 protein, human; C497684:Fmr1 protein, mouse