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A family of cold-regulated RNA-binding protein genes in the cyanobacterium Anabaena variabilis M3.

ABSTRACT: I previously found a cold-regulated RNA-binding protein gene rbpA (now named rbpA1) in Anabaena variabilis M3 [Sato, N. (1994) Plant Mol. Biol. 24, 819-823]. I show here that this gene is a member of a gene family containing at least eight members as evidenced by Southern blot and immunoblot analyses. I have isolated three additional genes (rbpB, rbpC and rbpD) in this family. Of these, rbpB was 100% identical to the rbpB gene of Anabaena 7120 reported previously. Another gene named rbpA in Anabaena 7120 was also found to exist in A.variabilis M3 with identical sequence and named rbpA2. The amino acid sequences of these gene products were highly conserved, except that the RbpD protein lacked glycine-rich C-terminal domain present in all other known members of the gene family. RNA blot and immunoblot analyses showed that the expression of rbpA1, rbpA2, rbpB, rbpC and rbpD, as well as uncloned rbp genes was regulated by cold, though the exact time-course and extent of response to cold were different among these genes. Gel-filtration assay showed that all of the Rbp proteins have higher affinities to poly(G) and poly(U) than to poly(A) and poly(C).

SUBMITTER: Sato N

PROVIDER: S-EPMC307003 | biostudies-other | 1995 Jun

REPOSITORIES: biostudies-other

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A family of cold-regulated RNA-binding protein genes in the cyanobacterium Anabaena variabilis M3.

Sato N N

Nucleic acids research 19950601 12

I previously found a cold-regulated RNA-binding protein gene rbpA (now named rbpA1) in Anabaena variabilis M3 [Sato, N. (1994) Plant Mol. Biol. 24, 819-823]. I show here that this gene is a member of a gene family containing at least eight members as evidenced by Southern blot and immunoblot analyses. I have isolated three additional genes (rbpB, rbpC and rbpD) in this family. Of these, rbpB was 100% identical to the rbpB gene of Anabaena 7120 reported previously. Another gene named rbpA in Anab ...[more]

PMID: 7541909

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Project description:UnlabelledIn the cyanobacterium Anabaena variabilis ATCC 29413, aerobic nitrogen fixation occurs in micro-oxic cells called heterocysts. Synthesis of nitrogenase in heterocysts requires expression of the large nif1 gene cluster, which is primarily under the control of the promoter for the first gene, nifB1. Strong expression of nifH1 requires the nifB1 promoter but is also controlled by RNA processing, which leads to increased nifH1 transcript stability. The processing of the primary nifH1 transcript occurs at the base of a predicted stem-loop structure that is conserved in many heterocystous cyanobacteria. Mutations that changed the predicted secondary structure or changed the sequence of the stem-loop had detrimental effects on the amount of nifH1 transcript, with mutations that altered or destabilized the structure having the strongest effect. Just upstream from the transcriptional processing site for nifH1 was the promoter for a small antisense RNA, sava4870.1. This RNA was more strongly expressed in cells grown in the presence of fixed nitrogen and was downregulated in cells 24 h after nitrogen step down. A mutant strain lacking the promoter for sava4870.1 showed delayed nitrogen fixation; however, that phenotype might have resulted from an effect of the mutation on the processing of the nifH1 transcript. The nifH1 transcript was the most abundant and most stable nif1 transcript, while nifD1 and nifK1, just downstream of nifH1, were present in much smaller amounts and were less stable. The nifD1 and nifK1 transcripts were also processed at sites just upstream of nifD1 and nifK1.ImportanceIn the filamentous cyanobacterium Anabaena variabilis, the nif1 cluster, encoding the primary Mo nitrogenase, functions under aerobic growth conditions in specialized cells called heterocysts that develop in response to starvation for fixed nitrogen. The large cluster comprising more than a dozen nif1 genes is transcribed primarily from the promoter for the first gene, nifB1; however, this does not explain the large amount of transcript for the structural genes nifH1, nifD1, and nifK1, which are also under the control of the distant nifB1 promoter. Here, we demonstrate the importance of a predicted stem-loop structure upstream of nifH1 that controls the abundance of nifH1 transcript through transcript processing and stabilization and show that nifD1 and nifK1 transcripts are also controlled by transcript processing.

Dataset Information

A family of cold-regulated RNA-binding protein genes in the cyanobacterium Anabaena variabilis M3.

Publications

A family of cold-regulated RNA-binding protein genes in the cyanobacterium Anabaena variabilis M3.

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