Identification of a glialblastoma cell differentiation factor-related gene mRNA in human microvascular endothelial cells

A genomewide analysis of genes for the heat shock protein 70 chaperone system in the ascidian Ciona intestinalis

Molecular chaperones play crucial roles in various aspects of the biogenesis and maintenance of proteins in the cell. The heat shock protein 70 (HSP70) chaperone system, in which HSP70 proteins act as chaperones, is one of the major molecular chaperone systems conserved among a variety of organisms. To shed light on the evolutionary history of the constituents of the chordate HSP70 chaperone system and to identify all of the components of the HSP70 chaperone system in ascidians, we carried out a comprehensive survey for HSP70s and their cochaperones in the genome of Ciona intestinalis. We characterized all members of the Ciona HSP70 superfamily, J-proteins, BAG family, and some other types of cochaperones. The Ciona genome contains 8 members of the HSP70 superfamily, all of which have human and protostome counterparts. Members of the STCH subfamily of the HSP70 family and members of the HSPA14 subfamily of the HSP110 family are conserved between humans and protostomes but were not found in Ciona. The Ciona genome encodes 36 J-proteins, 32 of which belong to groups conserved in humans and protostomes. Three proteins seem to be unique to Ciona. J-proteins of the RBJ group are conserved between humans and Ciona but were not found in protostomes, whereas J-proteins of the DNAJC14, ZCSL3, FLJ13236, and C21orf55 groups are conserved between humans and protostomes but were not found in Ciona. J-proteins of the sacsin group seem to be specific to vertebrates. There is also a J-like protein without a conserved HPD tripeptide motif in the Ciona genome. The Ciona genome encodes 3 types of BAG family proteins, all of which have human and protostome counterparts (BAG1, BAG3, and BAT3). BAG2 group is conserved between humans and protostomes but was not found in Ciona, and BAG4 and BAG5 groups seem to be specific to vertebrates. Members for SIL1, UBQLN, UBADC1, TIMM44, GRPEL, and Magmas groups, which are conserved between humans and protostomes, were also found in Ciona. No Ciona member was retrieved for HSPBP1 group, which is conserved between humans and protostomes. For several groups of the HSP70 superfamily, J-proteins, and other types of cochaperones, multiple members in humans are represented by a single counterpart in Ciona. These results show that genes of the HSP70 chaperone system can be distinguished into groups that are shared by vertebrates, Ciona, and protostomes, ones shared by vertebrates and protostomes, ones shared by vertebrates and Ciona, and ones specific to vertebrates, Ciona, or protostomes. These results also demonstrate that the components of the HSP70 chaperone system in Ciona are similar to but simpler than those in humans and suggest that changes of the genome in the lineage leading to humans after the separation from that leading to Ciona increased the number and diversity of members of the HSP70 chaperone system. Changes of the genome in the lineage leading to Ciona also seem to have made the HSP70 chaperone system in this species slightly simpler than that in the common ancestor of humans and Ciona.

AIRE recruits multiple transcriptional components to specific genomic regions through tethering to nuclear matrix

Thymic selection requires that diverse self antigens be presented to developing thymocytes by stromal cells. Consistent with this function, medullary thymic epithelial cells have been shown to express a large number of genes, many of which are tissue restricted. Autoimmune regulator (AIRE) is a nuclear protein, which has recently been identified as a regulator of this process, however, the mechanism by which AIRE functions is not well understood. Here we use a transrepression assay to demonstrate that AIRE interacts with multiple components of the transcription complex including a novel interaction with the UBA domain protein, GBDR1. When AIRE is expressed in cultured human thymic epithelial cells, it tightly associates with nuclear matrix, suggesting that AIRE responsive genes may be localized to specific regions. Using a mathematical approach we have re-analyzed an Affymetrix dataset identifying AIRE responsive genes and show that they tend to localize to specific regions of the genome. Together, these data suggest that AIRE regulates gene expression by recruiting components of the transcription complex to specific regions of the genome via interactions with nuclear matrix.

Cytoplasmic ubiquitin ligase KPC regulates proteolysis of p27(Kip1) at G1 phase

The cyclin-dependent kinase inhibitor p27(Kip1) is degraded at the G0-G1 transition of the cell cycle by the ubiquitin-proteasome pathway. Although the nuclear ubiquitin ligase (E3) SCF(Skp2) is implicated in p27(Kip1) degradation, proteolysis of p27(Kip1) at the G0-G1 transition proceeds normally in Skp2(-/-) cells. Moreover, p27(Kip1) is exported from the nucleus to the cytoplasm at G0-G1 (refs 9-11). These data suggest the existence of a Skp2-independent pathway for the degradation of p27(Kip1) at G1 phase. We now describe a previously unidentified E3 complex: KPC (Kip1 ubiquitination-promoting complex), consisting of KPC1 and KPC2. KPC1 contains a RING-finger domain, and KPC2 contains a ubiquitin-like domain and two ubiquitin-associated domains. KPC interacts with and ubiquitinates p27(Kip1) and is localized to the cytoplasm. Overexpression of KPC promoted the degradation of p27(Kip1), whereas a dominant-negative mutant of KPC1 delayed p27(Kip1) degradation. The nuclear export of p27(Kip1) by CRM1 seems to be necessary for KPC-mediated proteolysis. Depletion of KPC1 by RNA interference also inhibited p27(Kip1) degradation. KPC thus probably controls degradation of p27(Kip1) in G1 phase after export of the latter from the nucleus.

Cloning and structural characterization of ECTACC, a new member of the transforming acidic coiled coil (TACC) gene family: cDNA sequence and expression analysis in human microvascular endothelial cells

Erythropoietin (Epo) transduces mitogenic and chemoattractant signals to human endothelial cells. Identifications of Epo-responsive genes are important for understanding the molecular nature of Epo signaling in endothelial cells. The effects of Epo on differential expression of various genes were examined in human microvascular endothelial cells (HMVEC) by differential display reverse transcriptase polymerase chain reaction (RT-PCR). In the current study we obtained from Epo-treated HMVEC a cDNA fragment with characteristics of the 3' end of mRNA. Using the cDNA fragment, we then selectively isolated a full-length clone by screening an unamplified endothelial cell cDNA library followed by 5' rapid amplification of cDNA ends by polymerase chain reaction (RACE-PCR). The nucleotide sequence of the longest cDNA revealed an open reading frame of 3311 nucleotides that encodes a protein consisting of approximately 906 amino acids with a predicted MW of approximately 100 kDa. The nucleotide sequence of the cDNA is nearly identical to that of transforming acidic coiled coil-containing (TACC2) and anti-zuai-1 (AZU-1) cDNA clones except at the 5'- and 3'-ends. Northern blot analysis showed an increase in endothelial-TACC-related mRNA levels in Epo-treated cells in comparison to that of the control cells. Endothelial-TACC-related mRNA was highly expressed in heart and skeletal muscle tissue. Placenta and brain tissue exhibited low levels of expression of endothelial-TACC-related gene. Southern blot analysis of genomic DNA from somatic cell hybrids showed that endothelial-TACC-related cDNA maps to chromosome 10. Immunofluorescence microscopy and the occurrence of several putative phosphorylation and SH3 binding sites on the deduced protein suggest that endothelial-TACC-related protein may be involved in Epo signaling cascades in endothelial cells.