Evolution and function of the neisserial dam‐replacing gene

Abstract

Phase variation through slippage-like mechanisms involving homopolymeric tracts depends in part on the absence of Dam-methylase in several pathogenic isolates of Neisseria meningitidis. In Dam-defective strains drg (dam-replacing gene), flanked by pseudo-transposable small repeated elements (SREs), replaced dam. We demonstrate that drg encodes a restriction endonuclease (NmeBII) that cleaves 5P P-GmeATC-3P P. drg is also present in 50% of Neisseria lactamica strains, but in most of them it is inactive because of the absence of an SRE-providing promoter. This is associated with the presence of GATmeC, suggesting an alternative restriction-modification system (RM) specific for 5P P-GATC-3P P, similar to Sau3AI-RM of Staphylococcus aureus 3A, Lactococcus lactis KR2 and Listeria monocytogenes. ß 2001 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.

A Retromerlike Complex Is a Novel Rab7 Effector That Is Involved in the Transport of the Virulence Factor Cysteine Protease in the Enteric Protozoan ParasiteEntamoeba histolytica

“…In contrast, overexpression of the dominant negative GDP-locked Rab7 caused diffusion of lysosomes to the periphery of the cells and decrease of EGF and LDL degradation (Bucci et al, 2000). Similar effects were also observed in overexpression of Rab7 effectors, i.e., rabinteracting lysosomal protein (RILP; Cantalupo et al, 2001) and Rab7-interacting RING finger protein (Rabring7; Mizuno et al, 2003). In contrast to mammalian Rab7, which is mainly associated with the acidic compartment (Bucci et al, 2000), Ͻ50% of GFP-EhRab7A-positive vacuoles were Lysotracker positive ( Figure 1A), suggesting that EhRab7A is not primarily localized to late endosomes or lysosomes.…”

“…This EhRab7A/ EhVps26-expressing transformant showed normal morphology of lysosomes and a total acidity as measured with a Lysotracker staining (unpublished data). In mammalian cells, the GTP-Rab7 overexpression did not influence the EGF degradation, whereas RILP and Rabring7 caused accumulation of lysosomes but showed reverse effects on EGF degradation (Bucci et al, 2000;Cantalupo et al, 2001;Mizuno et al, 2003). Quantitative immunoblot analysis of CP1, 2, and 5 in these transformants with specific antibodies showed that the amount of these CP proteins was slightly, but not significantly, reduced in EhRab7A-overexpressing transformant (unpublished data).…”

“…Homology-based genome-wide search of the putative effectors of the amoebic Rab7A using known Rab7 effectors from other organisms, including RILP, Rabring7, hVps34p/p150 (phosphatidylinositol 3-kinase), and proteasome ␣-subunit (XAPC7) indicated that this organism possesses homologues for Vps34/p150 and XAPC7, but lacks RILP and Rabring7, suggestive of the presence of novel Rab7 effectors in this organism (Cantalupo et al, 2001;Mizuno et al, 2003;Stein et al, 2003;Dong et al, 2004). Thus, we attempted to isolate the effector molecules of EhRab7A by affinity purification to gain an insight in the regulation of the amoebic Rab7A.…”

The Oxysterol-binding Protein Homologue ORP1L Interacts with Rab7 and Alters Functional Properties of Late Endocytic Compartments

“…The present finding is consistent with this and shows that, even though the clustering of LEs induced by ORP1L, ANK, and ANKϩPHD is not fully reversed by microtubule dissociation, the large clusters in the juxtanuclear region are microtubule dependent. Other Rab7 binding partners identified so far include RILP, a protein that links Rab7-positive LEs to microtubule-dependent dynein/dynactin motor complexes and has strong effects on LE/lysosomal transport (Cantalupo et al, 2001;Jordens et al, 2001); Rabring7, which affects epidermal growth factor degradation and causes perinuclear aggregation of lysosomes (Mizuno et al, 2003); and the phosphatidylinositol 3Ј-kinase VPS34 and its adaptor protein p150 (Stein et al, 2003). The clustering of LEs/lysosomes induced by ORP1L and its ANK and ANKϩPHD fragments resembles the effects of RILP or Rabring7 overexpression or that of Rab7 itself (Bucci et al, 2000).…”

“…The GTPase Rab7 is present on LEs and lysosomes (Chavrier et al, 1990;Meresse et al, 1995) and controls membrane trafficking between early and late endosomes and from LEs to lysosomes (Feng et al, 1995;Press et al, 1998). Rab7 also regulates the microtubule-dependent motility of late endocytic compartments (Cantalupo et al, 2001;Jordens et al, 2001;Lebrand et al, 2002;Harrison et al, 2003). In addition, Rab7 has been connected to a variety of LE functions, such as cellular vacuolization induced by Helicobacter pylori (Papini et al, 1997;Li et al, 2004), intracellular replication of Salmonella (Guignot et al, 2004;Harrison et al, 2004;Marsman et al, 2004), maturation of phagosomes Vieira et al, 2003;Ng Yan Hing et al, 2004), formation of autophagic vacuoles (Gutierrez et al, 2004;Jager et al, 2004), internalization/degradation of nutrient receptors (Edinger et al, 2003), and cholesterol and sphingolipid egress from LEs (Choudhury et al, 2002).…”