Rongo C (2001) Cytokine Growth Factor Rev "Disparate cell types use a shared complex of PDZ proteins for polarized protein localization."

Rongo C

[Cytokine Growth Factor Rev, 2001]

Based on their morphology and function, epithelial cells and neurons appear to have very little in common; however, growing evidence suggests that these two disparate cell types share an underlying polarization pathway responsible for sorting proteins to specific subcellular sites. An evolutionarily conserved complex of PDZ domain-containing proteins thought to be responsible for polarized protein localization has been identified from both brain and epithelial tissue, both from mammals and from the nematode C. elegans. Some of th most recent data on PDZ proteins and the proteins with which they interact are summarized. In particular, some of the more recently proposed models for their function in cells, and the in vivo and in vitro data that support these models are focused upon.

van Eenennaam H et al. (2000) IUBMB Life "Architecture and function of the human endonucleases RNase P and RNase MRP."

van Venrooij WJ, Pruijn GJ, Jarrous N, van Eenennaam H

[IUBMB Life, 2000]

In the past decade, important advances have been made in our knowledge of the composition of human RNase MRP and RNase P complexes. Both ribonucleoprotein particles function as endonucleases and contain RNA components that are structurally related. RNase MRP has been suggested to be involved in the processing of precursor rRNA; RNase P, in the maturation of tRNA. Here we give an overview of current data on the structure and function of human RNase MRP and RNase P particles, with emphasis on their molecular composition. At present, seven protein subunits, probably all associated with both ribonucleoprotein particles, have been isolated and their corresponding cDNAs cloned. Although no known structural motifs can be identified in the amino acid sequences of these proteins, the majority is clearly rich in basic residues. For two protein subunits, a cluster of basic amino acids have been shown to be involved in nucleolar accumulation, whereas another protein, which lacks such a region, probably enters the nucleolus by way of a piggyback mechanism. The binding regions for several of the protein subunits on the RNA have been identified, and the data have been used to create a putative structural model for the RNase MRP particle. The rather obscure situation concerning the association of the autoantigenic Th-40 protein and its possible relationship with one of the subunits, Rpp38, is discussed.