Plant Molecular Biology 36: 897–907, 1998.
1998 Kluwer Academic Publishers. Printed in Belgium.
Characterisation and promoter analysis of the Arabidopsis gene encoding
high-mobility-group protein HMG-I/Y
, Carl I. Webster
and John C. Gray
Department of Plant Sciences and Cambridge Centre for Molecular Recognition, University of Cambridge,
Downing Street, Cambridge CB2 3EA, UK (
author for correspondence);
Current address: Department of Plant
Biology, University of California, Berkeley, CA 94720, USA;
Current address: Cambridge Antibody Technology,
The Science Park, Melbourn, Royston SG8 6JJ, UK
Received 22 July 1997; accepted in revised form 26 November 1997
Key words: Arabidopsis thaliana, AT-hook, intron, transgenic tobacco plants
Thesingle-copygeneencodingtheArabidopsisHMG-I/Yproteinwas isolated andcharacterised. The geneencodes
a protein of 204 amino acid residues and contains a single intron of 73 bp. Primer extension analysis indicates
that transcription starts 115 bp upstream of the translation start and the leader sequence contains a short open
reading frame of 13 amino acid residues. The 5
-upstream region of 2117 bp and several 5
deletions were fused to
-glucuronidase (GUS) reporter gene and transferred to tobacco by Agrobacterium-mediated transformation.
Analysis of transgenic tobacco plants containing HMG-I/Y promoter regions of
the translation start detected GUS activity in all organs examined, including roots, stems, leaves and ﬂoral organs.
185 resulted in a 20–30-fold reduction in GUS activity in roots and stems, indicating the
presence of important quantitative regulatory elements in this region.
Abbreviations: AMV, avian myeloblastosis virus; EST, expressed sequence tag; GUS,
high mobility group; MU, 4-methylumbelliferone;MUG, 4-methylumbelliferyl
-glucuronide; ORF, open reading
The high-mobility-group (HMG) chromosomal pro-
proteins found in the nuclei of higher eukaryotes [5,
6]. HMG proteins were originally deﬁned as small
30 kDa) non-histone proteins which are extractable
from chromatin with 0.35 M sodium chloride and are
soluble in 2% trichloroacetic acid or 2–5% perchlor-
ic acid [5, 25]. Characterisation of cDNAs and genes
from animals has allowed the classiﬁcation into three
familiesof HMGproteins: HMG-1/2, HMG-14/17and
HMG-I/Y proteins [5, 6].
Thenucleotidesequencedatareportedwillappear in the EMBL,
GenBank and DDBJ Nucleotide Sequence Databases under the
accession number Y10836.
In plants, members of only the HMG-1/2 and
HMG-I/Y families have been identiﬁed . These
two classes of proteins are structurally distinct and
are characterised by DNA-binding domains called the
HMG box and the AT-hook, respectively . Plant
HMG-I/Y proteins consist of 170–213 amino acid
residues with 3 or 4 copies of the AT-hook motif [20,
28, 33, 36, 37, 47, 48]. They are similar to their mam-
malian counterparts only in the AT-hook regions .
The AT-hookbindsto the narrowminorgrooveof A/T-
rich DNA  and high-afﬁnity binding sites consist
of two or more appropriately spaced A/T tracts inter-
acting with two or more AT-hook motifs . Plant
HMG-I/Y proteins have been reported to interact with
A/T-rich regions of many plant promoters, including
those from the soybean nodulinN23 gene, the pea
ferredoxin gene , the oat phytochrome A3 gene