title: Helical repeats modular proteins are major players for organelle gene expression.
abstract: Mitochondria and chloroplasts are often described as semi-autonomous organelles because they have retained a genome. They thus require fully functional gene expression machineries. Many of the required processes going all the way from transcription to translation have specificities in organelles and arose during eukaryote history. Most factors involved in these RNA maturation steps have remained elusive for a long time. The recent identification of a number of novel protein families including pentatricopeptide repeat proteins, half-a-tetratricopeptide proteins, octotricopeptide repeat proteins and mitochondrial transcription termination factors has helped to settle long-standing questions regarding organelle gene expression. In particular, their functions have been related to replication, transcription, RNA processing, RNA editing, splicing, the control of RNA turnover and translation throughout eukaryotes. These families of proteins, although evolutionary independent, seem to share a common overall architecture. For all of them, proteins contain tandem arrays of repeated motifs. Each module is composed of two to three α-helices and their succession forms a super-helix. Here, we review the features characterising these protein families, in particular, their distribution, the identified functions and mode of action and propose that they might share similar substrate recognition mechanisms.
authors.affiliation: IBMP-CNRS, UPR2357, Strasbourg F-67084, France.
authors.forename: Kamel
authors.initials: K
authors.lastname: Hammani
authors.affiliation: IBMP-CNRS, UPR2357, Strasbourg F-67084, France.
authors.forename: Géraldine
authors.initials: G
authors.lastname: Bonnard
authors.affiliation: IBMP-CNRS, UPR2357, Strasbourg F-67084, France.
authors.forename: Ayoub
authors.initials: A
authors.lastname: Bouchoucha
authors.affiliation: IBMP-CNRS, UPR2357, Strasbourg F-67084, France.
authors.forename: Anthony
authors.initials: A
authors.lastname: Gobert
authors.affiliation: IBMP-CNRS, UPR2357, Strasbourg F-67084, France.
authors.forename: Franziska
authors.initials: F
authors.lastname: Pinker
authors.affiliation: IBMP-CNRS, UPR2357, Strasbourg F-67084, France.
authors.forename: Thalia
authors.initials: T
authors.lastname: Salinas
authors.affiliation: IBMP-CNRS, UPR2357, Strasbourg F-67084, France. Electronic address: giege@unistra.fr.
authors.forename: Philippe
authors.initials: P
authors.lastname: Giegé
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D002736:Chloroplasts / Q000235:genetics* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D008928:Mitochondria / Q000235:genetics* / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000235:genetics* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D010944:Plants / Q000235:genetics* / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017393:RNA Editing; D012326:RNA Splicing; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D024101:Mitochondrial Proteins; D010940:Plant Proteins; D014157:Transcription Factors
keywords: Half a tetratricopeptide; Mitochondrial transcription termination factor; Modular proteins; Octotricopeptide repeat; Pentatricopeptide repeat