Destabilization of tetraplex structures of the fragile X repeat sequence (CGG)n is mediated by homolog-conserved domains in three members of the hnRNP family.
Hairpin or tetrahelical structures formed by a d(CGG)n sequence in the FMR1 gene are thought to promote expansion of the repeat tract. Subsequent to this expansion FMR1 is silenced and fragile X syndrome ensues. The injurious effects of d(CGG)n secondary structures may potentially be countered by agents that act to decrease their stability. We showed previously that the hnRNP-related protein CBF-A destabilized G'2 bimolecular tetraplex structures of d(CGG)n. Analysis of mutant proteins revealed that the CBF-A-conserved domains RNP11 and ATP/GTP binding box were sufficient and necessary for G'2 d(CGG)n disruption while the RNP21 motif inhibited the destabilization activity. Here, we report that a C-terminal fragment of CBF-A whose only remaining conserved domain was the ATP/GTP binding motif, disrupted G'2 d(CGG)n more selectively than wild-type CBF-A. Further, two additional members of the hnRNP family, hnRNP A2 and mutant hnRNP A1 effectively destabilized G'2 d(CGG)n. Examination of mutant hnRNP A2 proteins revealed that, similar to CBF-A, their RNP11 element and ATP/GTP binding motif mediated G'2 d(CGG)n disruption, while the RNP21 element blocked their action. Similarly, the RNP11 and RNP21 domains of hnRNP A1 were, respectively, positive and negative mediators of G'2 d(CGG)n destabilization. Last, employing the same conserved motifs that mediated disruption of the DNA tetraplex G'2 d(CGG)n, hnRNP A2 destabilized r(CGG)n RNA tetraplex.
Khateb
Samer
S
Unit of Biochemistry, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, P.O. Box 9649, Haifa 31096, Israel.
Weisman-Shomer
Pnina
P
Hershco
Inbal
I
Loeb
Lawrence A
LA
Fry
Michael
M
D000255:Adenosine Triphosphate / Q000378:metabolism; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001665:Binding Sites; D017124:Conserved Sequence; D004247:DNA / Q000737:chemistry*; D051860:Fragile X Messenger Ribonucleoprotein 1; D054856:G-Quadruplexes; D006160:Guanosine Triphosphate / Q000378:metabolism; D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics*; D009690:Nucleic Acid Conformation; D017434:Protein Structure, Tertiary; D012313:RNA / Q000737:chemistry; D020871:RNA Stability; D016601:RNA-Binding Proteins; D012091:Repetitive Sequences, Nucleic Acid; D017386:Sequence Homology, Amino Acid
D000255:Adenosine Triphosphate; D004247:DNA; D051860:Fragile X Messenger Ribonucleoprotein 1; D006160:Guanosine Triphosphate; D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; D009419:Nerve Tissue Proteins; D012313:RNA; D016601:RNA-Binding Proteins; C439768:hnRNP A2