Stimulatory effect of the maize HMGa protein on reporter gene expression in maize protoplasts

Abstract

The high mobility group (HMG) proteins represent a class of chromosomal non‐histone proteins with an assumed influence on transcription. In this context, the effect of the maize HMGa protein on reporter gene expression was examined. Transient co‐transformation experiments in maize protoplasts with plasmid constructs directing the synthesis of the maize HMGa protein and with a luciferase reporter plasmid demonstrated a stimulatory effect of the HMGa protein on the reporter gene expression. Additional experiments with HMGa deletion constructs indicated that the HMG‐Box DNA‐binding motif is important for the observed effect, while the acidic carboxy‐terminal domain of the HMGa protein appears to be dispensable.

Chromosomal high mobility group (HMG) proteins of the HMGB-type occurring in the moss Physcomitrella patens

“…Plant HMGB proteins were also found to be involved in transcriptional regulation . They facilitate the DNA-binding of transcriptional regulators of the bZIP and Dof families (Grasser et al, 2007b;Krohn et al, 2002;Schultz et al, 1996;Yanagisawa, 1997), and the maize HMGB1 enhances reporter gene expression in cotransformed protoplasts (Grasser et al, 1993). In the majority of reported cases, HMGB proteins stimulate transcription.…”

Stability of the maize chromosomal high-mobility-group proteins, HMGa and HMGb,in vivo

“…50-120 h depending on experimental conditions and cell type In line with the observed stability, the amino acid sequence of the maize H M G a protein [5] displays no destabilizing PEST sequences [22,23] and has a potentially stabilizing N-terminus corresponding to the N-end rule [ 1 ]. The stability of the H M G a protein of BMS cells could also be an explanation for the lack of function of the H M G a antisense construct in transient cotransformation assays performed in the same cell culture [7]. The stability of the H M G proteins in the intact cell is in contrast to their sensitivity to the attack of proteases during the purification from animal [ 24] and plant [6] tissues.…”

“…In maize, a preferential binding of the two larger of the four major H M G proteins, H M G a and HMGb, to CCAAT and TATA boxes of the zein storage protein gene pMS1 has been observed [8]. Furthermore, a stimulatory effect on the expression of a co-transformed reporter gene could be demonstrated in transient transformation assays with a plasmid expressing the H M G a protein [7], which belongs to the vertebrate HMG1 protein family displaying an HMGbox DNA-binding motif and a highly acidic carboxy-terminal domain [ 5 ]. The DNA-binding domain of the H M G a protein was essential for the observed effect, while the acidic domain appeared to be dispensable in this context [7].…”

“…Furthermore, a stimulatory effect on the expression of a co-transformed reporter gene could be demonstrated in transient transformation assays with a plasmid expressing the H M G a protein [7], which belongs to the vertebrate HMG1 protein family displaying an HMGbox DNA-binding motif and a highly acidic carboxy-terminal domain [ 5 ]. The DNA-binding domain of the H M G a protein was essential for the observed effect, while the acidic domain appeared to be dispensable in this context [7]. As the transient transformation assays indicated a rather high stability of the endogenous H M G proteins and since no data were available on this subject with the exception of some studies on the stability of animal HMG1/2 proteins [2,21], we analyzed here in more detail the stability of the maize H M G a and H M G b proteins in vivo.…”

Endosperm Box Binding Proteins: cDNA Cloning of a Wheat HMG Protein

“…10/199611 16 DNA-bending and binds to AfT-rich doublestranded linear DNA and to four-way junction DNA (19). In transient transformation assays performed in maize protoplasts, the HMGa protein has a weak stimulatory effect on the expression of a reporter gene controlled by the maize shrunken promoter (17). As for the animal HMG 1 protein, the functions of these proteins are only poorly understood.…”