Biomedical subjects

Ho Chul Kang

Publications and source records attributed to Ho Chul Kang.

5 recordsLinked to original sources

PubMed2006

Jak2 and Tyk2 are necessary for lineage-specific differentiation, but not for the maintenance of self-renewal of mouse embryonic stem cells.

As the LIF-induced Jak1/STAT3 pathway has been reported to play a crucial role in self-renewal of mESCs, we sought to determine if Jak2, which is also expressed in mESCs, might also be involved in the pathway. By employing an RNAi strategy, we established both Jak2 and Jak2/Tyk2 knockdown mESC clones. Both Jak2 and Jak2/Tyk2 knockdown clones maintained the undifferentiated state as wild-type controls, even in a very low concentration of LIF. However, we observed not only faster onset of differentiation but also differential expression of tissue-specific lineage genes for ectodermal and mesodermal, but not endodermal origins from embryoid bodies generated from both types of knockdown clones compared to the wild-type. Furthermore, the reduced level of Jak2 caused differentiation of mESCs in the presence of LIF when the Wnt pathway was activated by LiCl treatment. Taken together, we demonstrated that Jak2 and Tyk2 are not involved in LIF-induced STAT3 pathway for self-renewal of mESCs, but play a role in early lineage decision of mESCs to various differentiated cell types.

Animals↗

PubMed2006

Profiling of differentially expressed genes in human stem cells by cDNA microarray.

Stem cells are unique cell populations with the ability to undergo both self-renewal and differentiation, although a wide variety of adult stem cells as well as embryonic stem cells have been identified and stem cell plasticity has recently been reported. To identify genes implicated in the control of the stem cell state as well as the characteristics of each stem cell line, we analyzed the expression profiles of genes in human embryonic, hematopoietic (CD34+ and CD133+), and mesenchymal stem cells using cDNA microarrays, and identified genes that were differentially expressed in specific stem cell populations. In particular we were able to identify potential hESC signature-like genes that encode transcription factors (TFAP2C and MYCN), an RNA binding protein (IMP-3), and a functionally uncharacterized protein (MAGEA4). The overlapping sets of 22 up-regulated and 141 down-regulated genes identified in this study of three human stem cell types may also provide insight into the developmental mechanisms common to all human stem cells. Furthermore, our comprehensive analyses of gene expression profiles in various adult stem cells may help to identify the genetic pathways involved in self-renewal as well as in multi-lineage specific differentiation.

Adult↗

PubMed2005

Identification and characterization of four novel peptide motifs that recognize distinct regions of the transcription factor CP2.

Although ubiquitously expressed, the transcriptional factor CP2 also exhibits some tissue- or stage-specific activation toward certain genes such as globin in red blood cells and interleukin-4 in T helper cells. Because this specificity may be achieved by interaction with other proteins, we screened a peptide display library and identified four consensus motifs in numerous CP2-binding peptides: HXPR, PHL, ASR and PXHXH. Protein-database searching revealed that RE-1 silencing factor (REST), Yin-Yang1 (YY1) and five other proteins have one or two of these CP2-binding motifs. Glutathione S-transferase pull-down and coimmunoprecipitation assays showed that two HXPR motif-containing proteins REST and YY1 indeed were able to bind CP2. Importantly, this binding to CP2 was almost abolished when a double amino acid substitution was made on the HXPR sequence of REST and YY1 proteins. The suppressing effect of YY1 on CP2's transcriptional activity was lost by this point mutation on the HXPR sequence of YY1 and reduced by an HXPR-containing peptide, further supporting the interaction between CP2 and YY1 via the HXPR sequence. Mapping the sites on CP2 for interaction with the four distinct CP2-binding motifs revealed at least three different regions on CP2. This suggests that CP2 recognizes several distinct binding motifs by virtue of employing different regions, thus being able to interact with and regulate many cellular partners.

Amino Acid Sequence↗

PubMed2005

Erythroid cell-specific alpha-globin gene regulation by the CP2 transcription factor family.

We previously demonstrated that ubiquitously expressed CP2c exerts potent erythroid-specific transactivation of alpha-globin through an unknown mechanism. This mechanism is reported here to involve specific CP2 splice variants and protein inhibitor of activated STAT1 (PIAS1). We identify a novel murine splice isoform of CP2, CP2b, which is identical to CP2a except that it has an additional 36 amino acids encoded by an extra exon. CP2b has an erythroid cell-specific transcriptional activation domain, which requires the extra exon and can form heteromeric complexes with other CP2 isoforms, but lacks the DNA binding activity found in CP2a and CP2c. Transcriptional activation of alpha-globin occurred following dimerization between CP2b and CP2c in erythroid K562 and MEL cells, but this dimerization did not activate the alpha-globin promoter in nonerythroid 293T cells, indicating that an additional erythroid factor is missing in 293T cells. PIAS1 was confirmed as a CP2 binding protein by the yeast two-hybrid screen, and expression of CP2b, CP2c, and PIAS1 in 293T cell induced alpha-globin promoter activation. These results show that ubiquitously expressed CP2b exerts potent erythroid cell-specific alpha-globin gene expression by complexing with CP2c and PIAS1.

Alternative Splicing↗

PubMed2004

Transcription factor CP2 is involved in activating mBMP4 in mouse mesenchymal stem cells.

CP2 is a member of a family of transcription factors that regulate genes involved in events from early development to terminal differentiation. In an effort to understand how it selects its target genes we carried out a database search, and located several CP2 binding motifs in the promoter region of bone morphogenetic protein-4 (BMP4). BMP4 is a key regulator of cell fate and body patterning throughout development. For the CP2 binding motifs in BMP4 promoter region to be relevant in vivo, CP2 and BMP4 should be expressed together. We found that CP2b and CP2c, two potent transcriptional activators, are expressed in a manner similar to BMP4 during osteoblast differentiation of C3H10T1/2 cells. In in vitro assays, the CP2 proteins bound to two CP2 binding motifs (-715 to -676 and -147 to -118) in the BMP4 promoter, and luciferase reporter assays indicated that this binding was essential for transcription of BMP4 during osteoblast differentiation. Taken together, our data indicate that CP2b and CP2c play important roles during bone development by activating BMP4 transcription.

Animals↗