Comparative analysis of chromosomal HMG proteins from monocotyledons and dicotyledons

Abstract

Chromosomal high-mobility-group (HMG) proteins occur ubiquitously in eukaryotes and their common structural and biochemical features indicate a critical role. In this context, we compared structural and functional aspects of HMG proteins from the monocotyledonous plant maize and the dicotyledonous plant Vicia faba. Besides biochemical similarities and immunological differences found between these proteins, the isolation and characterization of a cDNA encoding the V. faba homologue of the maize HMGa protein revealed great similarities between these two proteins, including the HMG-box DNA-binding motif and an acidic domain. Therefore, like the maize HMGa protein, the V. faba HMG protein belongs to the vertebrate HMG1 family, which consists of HMG proteins and transcription factors of various eukaryotes.

Gene discovery in the wood-forming tissues of poplar: Analysis of 5,692 expressed sequence tags

“…Several other highly abundant transcripts were moderately similar (scores between 100 and 250) to cyclophilin, translationally controlled tumor protein, blue copper protein, and ADP-ribosylation factor. The EST annotated as high-mobility group (HMG) protein exhibited a low similarity to other HMG proteins (score of 94), but contained the highly conserved HMG domain (27), indicating that it probably encodes an HMG protein. The identity of the most highly abundant transcript in the developing-xylem library is ambiguous because it was similar both to nodulin, which is expressed during nodule formation in alfalfa (score 136), and to an extracellular glycoprotein in carrot (score 124).…”

An intrinsically bent region upstream of the transcription start site of the rRNA genes of Arabidopsis thaliana interacts with an HMG-related protein

“…Interestingly, one protein retained its binding activity to the 143 bp fragment even after incubation at 100 °C. This is a strong indication for the presence of an HMG-related protein, since H M G proteins from various species are known to tol- erate heat treatment up to 90 °C [7,8,13,21 ]. In addition, H M G proteins are generally defined to be soluble in 2 ~o trichloroacetic acid (TCA).…”

“…The protein that binds specifically to the bent 143 bp fragment is soluble in 1 ~o TCA, partially precipitated by 1.5~o TCA and completely insoluble in 2~o TCA. Although this operational definition for H M G proteins is not fully given, various observations support the assumption, that the unknown protein represents a HMG-related protein: ( 1 ) H M G proteins are known to be associated with transcriptionally active chromatin [28]; (2) they have been shown to bind to A/T-rich stretches in the 5'-flanking region or various genes [6,16,21]; (3)the vertebrate high-mobility-group proteins HMG1 and HMG2 are known to bind preferentially to prebent DNA [ 1,22] suggesting that H M G proteins in general recognize altered DNA structures rather than specific sequences; (4) a striking heat stability up to 90 °C was reported for H M G proteins of Viciafaba, maize, soybean and wheat [7,8,13,21]; the putative H M G protein of A. thaliana was shown to tolerate heat treatment up to 100 ° C; (5) the heat-stable protein was shown to have a molecular mass of 28.5 kDa and thus is in the upper range of wheat H M G proteins that are calculated to range in size from 14.5 kDa (HMGd) to 24.3 kDa (HMGa) [27]. Moreover, Moehs et aL [ 18 ] reported a lower electrophoretic mobility for A. thaliana H M G a compared to wheat HMGa.…”

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

“…In plants, H M G proteins have been isolated and partly characterized from various species [9,13,17,25,27,28]. The wheat and barley H M G proteins have been found to be associated with transcriptionally active chromatin [ 16,26].…”

“…The wheat and barley H M G proteins have been found to be associated with transcriptionally active chromatin [ 16,26]. Binding of several plant H M G proteins to A/T-rich DNA stretches frequently occurring in the 5'-flanking region of plant genes has been demonstrated in vitro [4,9,11,13,15,19]. 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].…”