The Arabidopsis MBD7 (AtMBD7) - a naturally occurring poly MBD protein - was previously found to be functional in binding methylated-CpG dinucleotides in vitro and localized to highly methylated chromocenters in vivo. Furthermore, AtMBD7 has significantly lower mobility within the nucleus conferred by cooperative activity of its three MBD motifs. Here we show that besides the MBD motifs, AtMBD7 possesses a strong chromatin binding domain located at its C-terminus designated sticky-C (StkC). Mutational analysis showed that a glutamic acid residue near the C-terminus is essential though not sufficient for the StkC function. Further analysis demonstrated that this motif can render nuclear proteins highly immobile both in plant and animal cells, without affecting their native subnuclear localization. Thus, the C-terminal, StkC motif plays an important role in fastening AtMBD7 to its chromosomal, CpG-methylated sites. It may be possible to utilize this motif for fastening nuclear proteins to their chromosomal sites both in plant and animal cells for research and gene therapy applications.
Bibliographical noteFunding Information:
We thank Y. Avivi for critical reading and editing of the manuscript, V. Kiss for confocal assistance, Y. Shav-Tal for providing the human U2OS cells and Avi Levy for hosting A.Z. and for discussion of results. This work was supported by a grant from The Israel Science Foundation (grant number 88192201 ), and by YEDA Research and Development Co. Ltd. A.Z. is a recipient of the Israeli Ministry of Science Eshkol Fellowship for Ph.D. students. L.K.P. was supported by a postdoctoral fellowship awarded by the Jacob Blaustein Center for Scientific Cooperation (BCSC).
- Chromatin binding
- Methyl-CpG-binding domain (MBD)
- Nuclear proteins
- Protein mobility