Journal of Cell Science, Vol 111, Issue 17 2615-2623, Copyright © 1998 by Company of Biologists

JOURNAL ARTICLES

Distinct domains of a nucleolar protein mediate protein kinase binding, interaction with nucleic acids and nucleolar localization

A Das, JH Park, CB Hagen and M Parsons
Seattle Biomedical Research Institute, Seattle, WA 98109, USA.

Nopp44/46 is a phosphoprotein of the protozoan parasite Trypanosoma brucei that is localized to the nucleolus. Based on the primary sequence, Nopp44/46 appears to be a protein composed of distinct domains. This communication describes the relationship of these domains to the known functional interactions of the molecule and suggests that the amino-terminal region defines a novel homology region that functions in nucleolar targeting. We have previously shown that Nopp44/46 is capable of interacting with nucleic acids and associating with a protein kinase. Using in vitro transcription and translation, we now demonstrate that the nucleic acid binding function maps to the carboxy-terminal domain of the molecule, a region rich in arginine-glycine-glycine motifs. Our experiments reveal that a central region containing a high proportion of acidic residues is required for association with the protein kinase. Analysis of transfectants expressing epitope-tagged Nopp44/46 deletion constructs showed that the amino-terminal 96 amino acids allowed nuclear and nucleolar accumulation of the protein. This region of the molecule shows homology to several recently described nucleolar proteins. Deletion of a 27-amino-acid region within this domain abrogated nucleolar, but not nuclear, localization. These studies show that Nopp44/46 is composed of distinct modules, each of which plays a different role in molecular interactions. We suggest that this protein could facilitate interactions between sets of nucleolar molecules.

This article has been cited by other articles:

				C. C. Goulah, M. Pelletier, and L. K. Read Arginine methylation regulates mitochondrial gene expression in Trypanosoma brucei through multiple effector proteins RNA, August 1, 2006; 12(8): 1545 - 1555. [Abstract] [Full Text] [PDF]

				B. C. Jensen, D. L. Brekken, A. C. Randall, C. T. Kifer, and M. Parsons Species Specificity in Ribosome Biogenesis: a Nonconserved Phosphoprotein Is Required for Formation of the Large Ribosomal Subunit in Trypanosoma brucei Eukaryot. Cell, January 1, 2005; 4(1): 30 - 35. [Abstract] [Full Text] [PDF]

				J. E. Lowell and G. A. M. Cross A variant histone H3 is enriched at telomeres in Trypanosoma brucei J. Cell Sci., November 15, 2004; 117(24): 5937 - 5947. [Abstract] [Full Text] [PDF]

				S van Koningsbruggen, R W Dirks, A M Mommaas, J J Onderwater, G Deidda, G W Padberg, R R Frants, and S M van der Maarel FRG1P is localised in the nucleolus, Cajal bodies, and speckles J. Med. Genet., April 1, 2004; 41(4): e46 - e46. [Full Text] [PDF]

				J. L. Dynes, S. Xu, S. Bothner, J. M. Lahti, and R. T. Hori The Carboxyl-Terminus Directs TAFI48 to the Nucleus and Nucleolus and Associates with Multiple Nuclear Import Receptors J. Biochem., March 1, 2004; 135(3): 429 - 438. [Abstract] [Full Text] [PDF]

				B. C. Jensen, Q. Wang, C. T. Kifer, and M. Parsons The NOG1 GTP-binding Protein Is Required for Biogenesis of the 60 S Ribosomal Subunit J. Biol. Chem., August 22, 2003; 278(34): 32204 - 32211. [Abstract] [Full Text] [PDF]

				J. Park, B. Jensen, C. Kifer, and M Parsons A novel nucleolar G-protein conserved in eukaryotes J. Cell Sci., January 1, 2001; 114(1): 173 - 185. [Abstract] [PDF]

				M Hoek, M Engstler, and G. Cross Expression-site-associated gene 8 (ESAG8) of Trypanosoma brucei is apparently essential and accumulates in the nucleolus J. Cell Sci., January 11, 2000; 113(22): 3959 - 3968. [Abstract] [PDF]

				A DeRocher, C. Hagen, J. Froehlich, J. Feagin, and M Parsons Analysis of targeting sequences demonstrates that trafficking to the Toxoplasma gondii plastid branches off the secretory system J. Cell Sci., January 11, 2000; 113(22): 3969 - 3977. [Abstract] [PDF]

				J. M. Waggener and P. J. DiMario Two Splice Variants of Nopp140 in Drosophila melanogaster Mol. Biol. Cell, January 1, 2002; 13(1): 362 - 381. [Abstract] [Full Text] [PDF]