DNA-interactions and nuclear localisation of the chromosomal HMG domain protein SSRP1 from maize.
The structure-specific recognition protein 1 (SSRP1) is a member of the protein family containing a high mobility group (HMG) domain DNA-binding motif. We have functionally characterised the 71.4 kDa Zm-SSRP1 protein from maize. The chromatin-associated Zm-SSRP1 is detected by immunoblot analysis in maize leaves, kernels and suspension culture cells, but not in roots. Mediated by its HMG domain, recombinant Zm-SSRP1 interacts structure-specifically with supercoiled DNA and DNA minicircles when compared with linear DNA. In linear duplex DNA, the protein does not recognise a specific sequence, but it binds preferentially to sequences containing the deformable dinucleotide TG, as demonstrated by a random oligonucleotide selection experiment. Zm-SSRP1 modulates DNA structure by bending the target sequence, since it promotes the circularisation of short DNA fragments in the presence of DNA ligase. Moreover, Zm-SSRP1 facilitates the formation of nucleoprotein structures, as measured using the bacterial site-specific beta-mediated recombination reaction. Analysis of the subcellular localisation of various SSRP1-GFP fusions revealed that, in contrast to HMG domain transcription factors, the nuclear localisation sequence of Zm-SSRP1 is situated within a 20-amino acid residue region adjacent to the HMG domain rather than within the DNA-binding domain. The results are discussed in the context of the likely function of SSRP1 proteins in transcription and replication.
Röttgers
K
K
Institut für Biologie III, Albert-Ludwigs-Universität Freiburg, Schänzlestr. 1, D-79104 Freiburg, Germany.
Krohn
N M
NM
Lichota
J
J
Stemmer
C
C
Merkle
T
T
Grasser
K D
KD
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism*; D002875:Chromosomes; D017931:DNA Primers; D018076:DNA, Complementary; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D006609:High Mobility Group Proteins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D003313:Zea mays / Q000378:metabolism*
D017931:DNA Primers; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins