Essential role for KH domains in RNA binding: impaired RNA binding by a mutation in the KH domain of FMR1 that causes fragile X syndrome.
The KH domain is an evolutionarily conserved sequence motif present in many RNA-binding proteins, including the pre-mRNA-binding (hnRNP) K protein and the fragile X mental retardation gene product (FMR1). We assessed the role of KH domains in RNA binding by mutagenesis of KH domains in hnRNP K and FMR1. Conserved residues of all three hnRNP K KH domains are required for its wild-type RNA binding. Interestingly, while fragile X syndrome is usually caused by lack of FMR1 expression, a previously reported mutation in a highly conserved residue of one of its two KH domains (Ile-304-->Asn) also results in mental retardation. We found that the binding of this mutant protein to RNA is severely impaired. These results demonstrate an essential role for KH domains in RNA binding. Furthermore, they strengthen the connection between fragile X syndrome and loss of the RNA binding activity of FMR1.
Siomi
H
H
Howard Hughes Medical Institute, University of Pennsylvania School of Medicine, Philadelphia 19104-6148.
Choi
M
M
Siomi
M C
MC
Nussbaum
R L
RL
Dreyfuss
G
G
D000595:Amino Acid Sequence; D051860:Fragile X Messenger Ribonucleoprotein 1; D005600:Fragile X Syndrome / Q000503:physiopathology*; D034641:Heterogeneous-Nuclear Ribonucleoprotein K; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins; D012261:Ribonucleoproteins / Q000737:chemistry; D013329:Structure-Activity Relationship
D051860:Fragile X Messenger Ribonucleoprotein 1; D034641:Heterogeneous-Nuclear Ribonucleoprotein K; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D009419:Nerve Tissue Proteins; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D012261:Ribonucleoproteins; C497683:FMR1 protein, human