The protein ZmWHY1, is the focus of this study. It is a gene involved in the chloroplast splicing machinery. So far nine nucleus encoded proteins that are necessary for the splicing of various subsets of the approximately 20 chloroplast introns in vascular plants have been reported. CRS1, is one of the first, and it is necessary for the splicing of the atpf intron. CRS1 binds specifically binds to that intron. Because of its size in vitro and that the fact that it is not sufficient to promote intron splicing in vivo, there must be other forms of proteins involved. Mass spectrometry was used to identify proteins that coimmuninoprecipitated with CRS1. They did find the ZmWHY1 gene coimmunoprecipated with CRS1. They were able to verify past research findings: WHY1 in dicots has been reported to be a ssDNA-binding protein that functions in the nucleus as both a transcription factor and as a negative regulator of telomere length. Arabidopsis WHY1 copurified with the ‘transcriptionally active chromosome’ from chloroplasts. There results add another layer to this complex picture. The research demonstrates that ZmWHY1 is essential for chloroplast biogenesis, and that it localizes to the chloroplast where it plays multiple roles in gene expression. Another role is added, RNA binding to WHY1’s repertoire of biochemical activities and demonstrate that ZmWHY1 is bound to a subset of chloroplast RNAs in chloroplast extract.
Terms to clarify:
coimmunoprecipitation: A purification procedure to determine if two different molecules (usually proteins) interact. An antibody specific to the protein of interest is added to a cell lysis. Then the antibody-protein complex is pelleted usually using protein-G sepharose which binds most antibodies. If there are any protein/molecules that bind to the first protein, they will also be pelleted. Identification of proteins in the pellet can be determined by western blot (if an antibody exist) or by sequencing a purified protein band.
Biogenesis: living things come from other living things
cited:
Jana Prikryl, Kenneth P. Watkins, Giulia Friso, Klaas J. van Wijk, and Alice Barkan1
Institute of Molecular Biology, University of Oregon, Eugene, OR 97405 and Department of Plant Biology, Cornell University, Ithaca, NY 14853, USA