J Appl Biomed 2:151-161, 2004 | DOI: 10.32725/jab.2004.018

Nucleolins from different model organisms have conserved sequences reflecting the conservation of key cellular functions through evolution

Fernando González-Camacho, Francisco Javier Medina^*

Centro de Investigaciones Biológicas (CSIC), Madrid, Spain

Sequences available in public protein databases belonging to nucleolin or nucleolin-like proteins have been aligned using public domain software, in order to obtain relevant data regarding the degree of their conservation, which could be a reflection of the degree of conservation of the functions currently attributed to this protein. Nucleolin is known to be a nucleolar multifunctional protein, involved in different steps of pre-rRNA transcription and processing. Three domains are constantly present in all nucleolins, namely a series of acidic/serin (Ac/Ser) sequences, a number of RNA recognition motifs (RRM) and a region rich in glycin and arginin (GAR). The number of motifs present in each one of the three domains is variable. Furthermore, we have characterized in all nucleolins the presence of a bipartite consensus nuclear localization sequence (NLS). The only cases in which this sequence with a definite structure was not totally evident were in the yeast S. pombe (a possible monopartite structure) and in the protozoan T. thermophyla, in which it appears to be absent. Finally, we have constructed the phylogenetic tree of the 15 species investigated, taking exclusively the data regarding this protein. Interestingly, the tree obtained closely resembles the organization of these taxonomic groups throughout evolution, as it is presently known. We conclude that nucleolin is a highly conserved protein, whose gene was already present in an ancestor eukaryotic species, at an early stage of the evolutionary process, from which it has evolved very slowly. This is a reflection of the fundamental functions carried out by this protein, which were already fixed in the ancestor species.

Keywords: nucleolar protein; nuclear localization sequence; RNA recognition motifs; glycin-arginin-rich; phylogenetic study; evolution

Received: May 18, 2004; Published: July 31, 2004  Show citation