The Core Promoter of Human Thioredoxin Reductase 1: CLONING, TRANSCRIPTIONAL ACTIVITY, AND Oct-1, Sp1, AND Sp3 BINDING REVEAL A HOUSEKEEPING-TYPE PROMOTER FOR THE AU-RICH ELEMENT-REGULATED GENE

Anna-Klara Rundlöf,Mattias Carlsten,Elias S.J Arnér

doi:10.1074/jbc.m101452200

Anna-Klara Rundlöf, Mattias Carlsten + Show 1 more

Open Access

https://doi.org/10.1074/jbc.m101452200

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Abstract

The selenoprotein thioredoxin reductase 1 (TrxR1) carries many vital antioxidant and redox regulatory functions. Its mRNA levels are known to be post-transcriptionally modulated via AUUUA motifs (AU-rich elements (AREs)), but the promoter yet remains unknown. Here we have cloned and determined the sequence of a 0.8-kilobase pair human genomic fragment containing the proximal promoter for TrxR1, which has transcriptional activity in several different cell types. The core promoter (-115 to +167) had an increased GC content and lacked TATA or CCAAT boxes. It contained a POU motif binding the Oct-1 transcription factor and two sites binding Sp1 and Sp3, which were identified with electrophoretic mobility shift assays using crude nuclear extracts of A549 cells. The TrxR1 promoter fulfills the typical criteria of a housekeeping gene. To our knowledge this is the first housekeeping-type promoter characterized for a gene with post-transcriptional regulation via ARE motifs generally possessed by transiently expressed proto-oncogenes, nuclear transcription factors, or cytokines and influencing mRNA stability in response to diverse exogenous factors. Expression of TrxR1 as an ARE-regulated housekeeping gene agrees with a role for the enzyme to maintain a balance between intracellular signaling via reactive oxygen species and protection of cells from excessive oxidative damage.

Highlights

The selenoprotein thioredoxin reductase 1 (TrxR1) carries many vital antioxidant and redox regulatory functions
Expression of TrxR1 as an ARE-regulated housekeeping gene agrees with a role for the enzyme to maintain a balance between intracellular signaling via reactive oxygen species and protection of cells from excessive oxidative damage
This is the first example of an ARE-regulated gene with transcription guided from a housekeeping-type promoter. We propose that this functional organization may be explained by the intimate link between intracellular signaling via reactive oxygen species [32, 35] and protection against oxidative damage, indicating a vital role played by TrxR1 for maintaining a functional balance in this regulation, and we propose the molecular mechanisms for how this can be achieved

Summary

The abbreviations used are

Thioredoxin; TrxR, thioredoxin reductase; UTR, untranslated region; ARE, AU-rich element; ROS, reactive oxygen species; nt, nucleotides; PIPES, 1,4-piperazinediethanesulfonic acid; kb, kilobase pair; PCR, polymerase chain reaction; bp, base pair(s). This is the first example of an ARE-regulated gene with transcription guided from a housekeeping-type promoter We propose that this functional organization may be explained by the intimate link between intracellular signaling via reactive oxygen species [32, 35] and protection against oxidative damage, indicating a vital role played by TrxR1 for maintaining a functional balance in this regulation, and we propose the molecular mechanisms for how this can be achieved.

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION