Chuanbing Zhu

WDR26: A novel Gβ‐like protein, suppresses MAPK signaling pathway

WD40 repeat proteins play important roles in a variety of cellular functions, including cell growth, proliferation, apoptosis, and intracellular signal transduction. Mitogen‐activated protein kinases (MAPKs) are evolutionary conserved enzymes in cell signal transduction connecting cell‐surface receptors to critical regulatory targets within cells and control cell survival, adaptation, and proliferation. Previous studies revealed that G‐protein coupled receptors (GPCRs) play important roles in the signal transduction from extracellular stimuli to MAPKs and the WD40‐containing Gβ proteins as well as Gβ‐like proteins are involved in the stimulation and regulation of the MAPK signaling pathways. Here we report the identification and characterization of a novel human WD40 repeat protein, WD40 repeat protein 26 (WDR26). The cDNA of WDR26 is 3,729 bp, encoding a Gβ‐like protein of 514 amino acids in the cytoplasm. The protein is highly conserved in evolution across different species from yeast, Drosophila, mouse, to human. Northern blot analysis indicates that WDR26 is expressed in most of the examined human tissues, especially at a high level in skeletal muscle. Overexpression of WDR26 in the cell inhibits the transcriptional activities of ETS proteins, ELK‐1 and c‐fos serum response element (SRE), mediated by MEKK1. These results suggest that WDR26 may act as a negative regulator in MAPK signaling pathway and play an important role in cell signal transduction.

Identification and characterization of two novel zinc finger genes, ZNF359 and ZFP28, in human development.

Transcription factors play an essential role in controlling gene expression during cardiac and vascular pathogeneses. Identification of regulatory genes in the cardiovascular system is a necessary step toward an understanding of the pathogenesis of congenital heart disease and acquired cardiovascular diseases. The Cys2/His2 type zinc finger genes are the single largest class of transcription factors in the human genome and many numbers of these krüpple-like zinc finger genes have been found to be involved in cardiac development or cardiovascular diseases. In this study, we have identified two novel human krüpple-like zinc finger genes named ZNF359 and ZFP28 from the human heart cDNA library. The complete human ZNF359 cDNA sequence is 3270bp and contains a 1932-bp open reading frame (ORF) that encodes a 643 amino acid protein with an N-terminal KRAB domain and 16 C-terminus zinc finger C2H2 motifs. The ZFP28 cDNA sequence is 4104bp and contains a 2076-bp ORF that encodes an 868 amino acid protein with an N-terminal signal peptide, two KRAB domains, and 14 C-terminal C2H2 zinc finger motifs. Northern blot analyses showed a strong expression of ZNF359 and ZFP28 in various tissues of adult human. A further analysis using human embryonic tissues (18-23 weeks) showed a development-specific expression pattern in heart, skeletal muscle, liver, lung, kidney, and brain, suggesting a role for these genes in embryonic development.

Expression of a novel Krüpple-like zinc-finger gene, ZNF382, in human heart.

With the aim of identifying genes involved in human heart development and disease, we have isolated a novel KRAB-related zinc-finger gene named ZNF382 from heart cDNA library. The ZNF382 gene has a predicted 548-amino acid open reading frame, encoding a putative 64kDa zinc-finger protein. The N-terminus of the ZNF382 coding region has a well-conserved Krüpple-associated box domain that consists of KRAB boxes A and B, whereas the C-terminus contains a Krüpple-type zinc-finger domain possessing nine C(2)H(2) zinc-finger motifs in tandem arrays. The ZNF382 gene is mapped to chromosome 19q13.13. Northern blot analysis indicates that a 2.9-kb transcript specific for ZNF382 is expressed at very early embryonic stage of human (at least earlier than gestation 34 day) and widely in human embryo tissues. At the adult stage, ZNF382 expression is restricted largely to heart tissue suggesting a potential role in heart development and function.

Expression of a novel member of sorting nexin gene family, SNX-L, in human liver development

The sorting nexin (SNX) protein family is implicated in the regulation of receptor degradation and membrane traffic in the cell. With the aim of identifying novel genes involved in receptor degradation and recycling, we have cloned a new member of the sorting nexin gene family, human sorting nexin L, SNX-L (or SNX21). This gene includes 4 exons and 3 introns, and is located on chromosome 20q12-13.1 region, encompassing 8 kb. The full-length cDNA of SNX-L is 1,811 bp, with an open reading frame of 1,092 bp. The protein consists of 364 amino acids and encodes a 40 kDa protein. The SNX-L protein has a common PX domain shared by all SNX family members. The similarity of SNX-L PX domain to the PX consensus sequence is over 40%. PX domains have been shown to associate with specific phospholipids and membrane compartments. Expression analysis of SNX-L mRNA indicates that SNX-L is distinctly and highly expressed in fetus liver, but only weakly expressed in brain, muscle (skeleton muscle, smooth muscle, and cardiac muscle), kidney, and adrenal gland. Strong liver expression of SNX-L is maintained from 12 to 25 weeks during human fetus development, suggesting that SNX-L may be a regulatory gene involved in receptor protein degradation during embryonic liver development.

A novel human SCAN/(Cys)2(His)2 zinc-finger transcription factor ZNF323 in early human embryonic development.

The C(2)H(2) zinc-finger motif found in many transcription factors is thought to be important for nucleic acid binding and/or dimerization. Here, we have identified and characterized a novel zinc-finger gene named ZNF323 using degenerate primers from an early human embryo heart cDNA library. The predicted protein contains six different C(2)H(2) type zinc fingers and a SCAN box. ZNF323 maps to chromosome 6p22.1-22.3. The expression levels were different during different development stages of human embryo between 15 and 23 weeks. Northern blot analysis shows that a 3.2-kb transcript specific for ZNF323 was expressed at high levels in the lung, liver, and kidney, while weakly expressed in intestine, brain, muscle, cholecyst, heart, and pancreas. In adult tissues, ZNF323 is expressed at high levels in liver and kidney, weakly in lung, pancreas, brain, placenta, muscle, and heart. Taken together, these results indicate that ZNF323 is a member of the zinc-finger transcription factor family and may be involved in the development of multiple embryonic organs.

Mapping the transcription repressive domain in the highly conserved human gene hnulp1

HNULP1, a new member of the basic helixloop-helix transcription factors, contains a DUF654 domain in its C-terminus and is highly conserved from Drosophilae, yeast, zebrafish to mouse. The function of this motif, however, is currently unknown. In this research, we fused five deletion fragments of the DUF654 domain to the GAL4 DNA-binding domain and then co-transfected with plasmids L8G5-Luc and VP-16. The analysis of the GAL4 luciferase reporter gene indicated that fragments from 228 to 407 amino acids in the DUF654 domain had a strong transcription repression activity. Therefore, this study lays a solid foundation for research on the mechanism of hnulp1 transcriptional regulation and the function of the DUF654 domain.