ABSTRACT ArsR is a well-studied transcriptional repressor that regulates microbe-arsenic interactions. Most microorganisms have an arsR gene, but in cases where multiple copies exist, the respective roles or potential functional overlap have not been explored. We examined the repressors encoded by arsR1 and arsR2 ( ars1 operon) and by arsR3 and arsR4 ( ars2 operon) in Agrobacterium tumefaciens 5A. ArsR1 and ArsR4 are very similar in their primary sequences and diverge phylogenetically from ArsR2 and ArsR3, which are also quite similar to one another. Reporter constructs ( lacZ ) for arsR1 , arsR2 , and arsR4 were all inducible by As(III), but expression of arsR3 (monitored by reverse transcriptase PCR) was not influenced by As(III) and appeared to be linked transcriptionally to an upstream lysR -type gene. Experiments using a combination of deletion mutations and additional reporter assays illustrated that the encoded repressors (i) are not all autoregulatory as is typically known for ArsR proteins, (ii) exhibit variable control of each other's encoding genes, and (iii) exert variable control of other genes previously shown to be under the control of ArsR1. Furthermore, ArsR2, ArsR3, and ArsR4 appear to have an activator-like function for some genes otherwise repressed by ArsR1, which deviates from the well-studied repressor role of ArsR proteins. The differential regulatory activities suggest a complex regulatory network not previously observed in ArsR studies. The results indicate that fine-scale ArsR sequence deviations of the reiterated regulatory proteins apparently translate to different regulatory roles. IMPORTANCE Given the significance of the ArsR repressor in regulating various aspects of microbe-arsenic interactions, it is important to assess potential regulatory overlap and/or interference when a microorganism carries multiple copies of arsR . This study explores this issue and shows that the four arsR genes in A. tumefaciens 5A, associated with two separate ars operons, encode proteins exhibiting various degrees of functional overlap with respect to autoregulation and cross-regulation, as well as control of other functional genes. In some cases, differences in regulatory activity are associated with only limited differences in protein primary structure. The experiments summarized herein also present evidence that ArsR proteins appear to have activator functions, representing novel regulatory activities for ArsR, previously known only to be a repressor.
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Discovering regulators in post transcriptional control of the biological clock of Neurospora crassa using Variable Topology Ensemble Methods on GPUs
In previous work we reconstructed the entire transcriptional network for all 2,418 clock-associated genes in the model filamentous fungus, N. crassa. Several authors have suggested that there is extensive post-transcriptional control in the genome-wide clock network (IEEE 3: 27, 2015). Here we have successfully reconstructed the entire clock network in N. crassa with a Variable Topology Ensemble Method (VTENS), assigning each clock-associated gene to the regulation of one or more of 5 transcription factors as well as to 6 RNA operons. The resulting network provides a unifying framework to explore the clock’s linkage to metabolism through post-transcriptional regulation, in which ~850 genes are predicted to fall under the regulatory control of an RNA operon. A unique feature of all of the RNA operons inferred is their functional connection to genes connected to the ribosome. We have been successful in distinguishing several hypotheses about regulatory topologies of the clock network through protein profiling of the regulators.
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- Award ID(s):
- 1713746
- NSF-PAR ID:
- 10075692
- Date Published:
- Journal Name:
- IEEE access
- Volume:
- 6
- ISSN:
- 2169-3536
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1109/ACCESS.2018.2871876
