Mitochondria-Localized Glutamic Acid-Rich Protein (MGARP) Gene Transcription Is Regulated by Sp1

Abstract

BackgroundMitochondria-localized glutamic acid-rich protein (MGARP) is a novel mitochondrial transmembrane protein expressed mainly in steroidogenic tissues and in the visual system. Previous studies showed that MGARP functions in hormone biosynthesis and its expression is modulated by the HPG axis.Methodology/Principal FindingsBy bioinformatics, we identified two characteristic GC-rich motifs that are located proximal to the transcription start site (TSS) of MGARP, and each contains two Specificity protein 1 (Sp1) binding elements. We then determined that the −3 kb proximal MGARP promoter is activated in a Sp1-dependent manner using reporter assays and knockdown of Sp1 led to decreased expression of endogenous MGARP messages. We also demonstrated that one of the two GC-rich motifs, GC-Box1, harbors prominent promoter activity mediated by Sp1, and that it requires both GC boxes for full transcriptional activation. These findings suggest a dominant role for these GC boxes and Sp1 in activating the MGARP promoter through a synergistic mechanism. Consistently, the results of an Electrophoretic Mobility Gel Shift Assay (EMSA) and Chromatin Immunoprecipitation (ChIP) confirmed that Sp1 specifically interacts with the GC-rich region. We further found that estrogen receptor α (ERα), a known Sp1 co-activator, could potentiate GC-boxes containing MGARP promoter activity and this effect is mediated by Sp1. Knockdown of Sp1 significantly diminished the MGARP promoter transactivation and the expression of endogenous MGARP mediated by both Sp1 and ERα.Conclusions/SignificanceThe present study identified a proximal core sequence in the MGARP promoter that is composed of two enriched Sp1 binding motifs and established Sp1 as one major MGARP transactivator whose functions are synergistic with ERα, providing a novel understanding of the mechanisms of MGARP gene transcriptional regulation.

Characterization of mitochondrial proteomes of nonbilaterian animals

“…Two other proteins were related to sperm mitochondrial processes: sperm mitochondrial‐associated cysteine‐rich protein (SMCP) and spermatogenesis‐associated protein 19 (SPATA19) . In addition, proteins not found in nonbilaterian taxa included hypoxia and HIF‐1‐induced mitochondrial protein (HUMMER), which is involved in mitochondrial transport and steroidogenesis , α‐synuclein (SNCA), a presynaptic protein known to modulate mitochondrial fusion and morphology and implicated in Parkinson's disease , and syntaphilin (SNPH), which is an outer‐mitochondrial membrane protein responsible for immobilizing mitochondria in axons (Supporting Information File S2). Given that these proteins were not identified in any nonbilaterian species, it would be interesting to investigate their origin and evolution by analysis of bilaterian mitochondrial proteomes.…”

A genomic atlas of human adrenal and gonad development

“…The 17 “novel” genes identified included MGARP (also known as OSAP ), DLK1 ( PREF1 ), and MAP3K15 ( ASK3 ). MGARP has been implicated in mitochondrial trafficking and steroidogenesis ( Jia et al , 2014 ; Jin et al , 2012 ; Zhou et al , 2011 ), but may also be a key target of OCT4 during reprogramming to pluripotency ( Tiemann et al , 2014 ). DLK1 is an imprinted gene that is involved in inhibiting adipocyte differentiation, which has previously been shown to be expressed in the outer undifferentiated zone of the male rat adrenal gland and signals to the adrenal capsule to regulate zonation ( Guasti et al , 2013 ).…”

A genomic atlas of human adrenal and gonad development

“…The 17 “novel” genes identified included MGARP (also known as OSAP ), DLK1 ( PREF1 ), and MAP3K15 ( ASK3 ). MGARP has been implicated in mitochondrial trafficking and steroidogenesis (Jia et al, 2014; Jin et al, 2012; Zhou et al, 2011), but may also be a key target of OCT4 during reprogramming to pluripotency (Tiemann et al, 2014). DLK1 is an imprinted gene that is involved in inhibiting adipocyte differentiation, which has previously been shown to be expressed in the outer undifferentiated zone of the male rat adrenal gland and signals to the adrenal capsule to regulate zonation (Guasti et al, 2013).…”