Affinity Profiles Categorize RNA-Binding Proteins into Distinctive Groups
Naomi Ueda,
Riki Kurokawa
Issue:
Volume 4, Issue 3, September 2018
Pages:
24-31
Received:
15 October 2018
Accepted:
31 October 2018
Published:
27 November 2018
Abstract: Recently, we have established a novel assay to detect interaction of RNA-binding proteins (RBPs) with RNA, using biotinylated RNA oligos to capture RBPs with Western blot of specific antibodies against RBPs. The assay detects RNA binding more confidently than the traditional gel shift assay. Starting with completely randomized RNA oligos from 5mer through 12mer length, their binding was examined with HeLa cell nuclear extract (NE). Coomassie brilliant blue-based (CBB) staining did not detect any strong signal. Western blot analysis of typical six RBP antibodies showed four RBPs bound with the random RNA oligos. hnRNPUL2 bound to all from 5mer to 12mer of RNA oligos, while no TLS and hnRNPH1 signal was detected in the random RNA oligo samples. Next, base specificity was examined using sets of oligos of RNA fixed at G, A, U, and C (GAUC RNA oliogs). The RNA oligos fixed at “G” (G RNA oligos) have the most prominent protein bands. A, U, and C of RNA oligos were shown to bind less numbers of protein. Western blot indicated that hnRNPUL2 and hnRNPU bind all four oligos of GAUC at the 10mer length. Contrarily, TLS and hnRNPH1 have no binding with these oligos of GAUC. Then, poly G, A, U and C of RNA at the length of 100mer were tested to see binding profile of RBPs. The CBB staining of the fractions bound with these four polymers of RNA showed that more bands were bound than GAUC RNA oligos. hnRNPU bound well to poly G, A, and, U, but slightly less to poly C. Intriguingly, TLS and hnRNPH1 have binding only to poly G, and also to their common specific sites consisting of GGUG motifs. These data demonstrate that RNA binding is regulated with three factors, length, base composition, and sequence. Furthermore, hnRNPU and hnRNPUL2 have low specificity binding to RNAs, while TLS and hnRNPH1 exert high specific binding. These different propensities in bindings of RBPs are supposed to support specific biological roles in living cells.
Abstract: Recently, we have established a novel assay to detect interaction of RNA-binding proteins (RBPs) with RNA, using biotinylated RNA oligos to capture RBPs with Western blot of specific antibodies against RBPs. The assay detects RNA binding more confidently than the traditional gel shift assay. Starting with completely randomized RNA oligos from 5mer ...
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