R1, a Novel Repressor of the Human Monoamine Oxidase A

Kevin Chen,Xiao-Ming Ou,Gao Chen,Si Ho Choi,Jean C Shih

doi:10.1074/jbc.m410033200

Kevin Chen, Xiao-Ming Ou + Show 3 more

Open Access

https://doi.org/10.1074/jbc.m410033200

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Abstract

Monoamine oxidase catalyzes the oxidative deamination of a number of neurotransmitters. A deficiency in monoamine oxidase A results in aggressive behavior in both humans and mice. Studies on the regulation of monoamine oxidase A gene expression have shown that the Sp1 family is important for monoamine oxidase A expression. To search for novel transcription factors, the sequences of three Sp1 sites in the monoamine oxidase A core promoter were used in the yeast one-hybrid system to screen a human cDNA library. A novel repressor, R1 (RAM2), has been cloned. The R1 cDNA encodes a protein with 454 amino acids and an open reading frame at the 5'-end. The transfection of R1 in a human neuroblastoma cell line, SK-N-BE (2)-C, inhibited the monoamine oxidase A promoter and enzymatic activity. The degree of inhibition of monoamine oxidase A by R1 correlated with the level of R1 protein expression. R1 was also found to repress monoamine oxidase A promoter activity within a natural chromatin environment. A gel-shift assay indicated that the endogenous R1 protein in SK-N-BE (2)-C cells interacted with the R1 binding sequence. R1 also bound directly to the natural monoamine oxidase A promoter in vivo as shown by chromatin immunoprecipitation assay. Immunocytochemical analysis showed that R1 was expressed in both cytosol and nucleus, which suggested a role for R1 in transcriptional regulation. Northern blot analysis revealed the presence of endogenous R1 mRNA in human brain and peripheral tissues. Taken together, this study shows that R1 is a novel repressor that inhibits monoamine oxidase A gene expression.

Highlights

Monoamine oxidase catalyzes the oxidative deamination of a number of neurotransmitters
This study shows that R1 is a novel repressor that inhibits monoamine oxidase A gene expression
A positive correlation has been found among cellular Sp1 concentration and Monoamine oxidase (MAO) A promoter and catalytic activity [17], which indicates that Sp1 is an activator of MAO A gene expression

Summary

Introduction

Monoamine oxidase catalyzes the oxidative deamination of a number of neurotransmitters. Mice deficient in MAO A have shown elevated amounts of brain serotonin, norepinephrine, and dopamine [9], no change in phenylethylamine [8], and display a distinct behavioral syndrome that includes enhanced aggression in males [10]. This is consistent with the impulsive aggression reported in men from a Dutch family with a MAO A deficiency [11]. MAO A/B double knock-out mice show increased baroreceptor response [14] and abnormal heart rate dynamics [15] These studies suggest that MAO A and B regulate many important biochemical functions and behaviors. The Sp1 motif in the MAO A core promoter was used as bait, and a novel repressor R1 of the human MAO A was cloned and characterized

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