Intraplastidial trafficking of a phage-type RNA polymerase is mediated by a thylakoid RING-H2 protein.

TitleIntraplastidial trafficking of a phage-type RNA polymerase is mediated by a thylakoid RING-H2 protein.
Publication TypeJournal Article
Year of Publication2008
AuthorsAzevedo, J, Courtois, F, Hakimi, M-A, Demarsy, E, Lagrange, T, Alcaraz, J-P, Jaiswal, P, Maréchal-Drouard, L, Lerbs-Mache, S
JournalProceedings of the National Academy of Sciences of the United States of America
Date Published2008 Jul 1
Keywords16S, Amino Acid Sequence, Arabidopsis, Arabidopsis Proteins, Bacteriophages, DNA-Binding Proteins, DNA-Directed RNA Polymerases, Gene Expression Regulation, Gene Library, Genetic, Intracellular Membranes, light, Messenger, Molecular Sequence Data, Organ Specificity, plant, Promoter Regions, Protein Binding, Protein Transport, Ribosomal, RNA, Saccharomyces cerevisiae Proteins, Thylakoids, Transcription Factors, Two-Hybrid System Techniques

The plastid genome of dicotyledonous plants is transcribed by three different RNA polymerases; an eubacterial-type enzyme, PEP; and two phage-type enzymes, RPOTp and RPOTmp. RPOTp plays an important role in chloroplast transcription, biogenesis, and mesophyll cell proliferation. RPOTmp fulfills a specific function in the transcription of the rrn operon in proplasts/amyloplasts during seed imbibition/germination and a more general function in chloroplasts during later developmental stages. In chloroplasts, RPOTmp is tightly associated with thylakoid membranes indicating that functional switching of RPOTmp is connected to thylakoid association. By using the yeast two-hybrid system, we have identified two proteins that interact with RPOTmp. The two proteins are very similar, both characterized by three N-terminal transmembrane domains and a C-terminal RING domain. We show that at least one of these proteins is an intrinsic thylakoid membrane protein that fixes RPOTmp on the stromal side of the thylakoid membrane, probably via the RING domain. A model is presented in which light by triggering the synthesis of the RING protein determines membrane association and functional switching of RPOTmp.