| Transcriptional regulation is an important part within the cell. Transcription factors bind specific DNA sequences, regulate expression of their target genes, and can be identified by the presence of their DNA binding domains. Transcription factors are pivotal in lineage commitment and differentiation in hematopoietic tissue. Hematopioesis is a highly regulated system giving rise to all mature blood cell types through a series of cell proliferations, commitment, and differentiation. Thus the objective of this study was to identify novel transcription factors and their associated proteins that participate in the transcriptional regulation of myeloid differentiation. By utilizing microarray technology and the genomic databases, the identification of transcription factors was done in a cell model of monocytic differentiation, and the identified proteins (1) contained motifs that were consistent with transcription factors, (2) were expressed in undifferentiated hematopoietic progenitor cells, and (3) had increased expression over time during differentiation. Using the U937 cells for our monocytic differentiation cell model, a total of 347 cDNAs was found that had increased expression during induced monocytic differentiation using GeneFilter filter array system. Of these, a total of eleven genes contained motifs consistent with transcription factors and other DNA binding domains. Of these selected genes, two were known transcription factors in myeloid differentiation-MAFB and PU.1, three novel zinc finger proteins, and 6 nuclear-DNA binding proteins. Next, real-time RT-PCR was used in an attempt to validate the expression patterns in our U937 cell model as well as another myeloid model system, HL60. For both known genes, their expression pattern was as predicted, and even MAFB was shown for the first lineage specificity toward monocytic differentiation in this system. For the three novel genes, the zinc fingers, their expression pattern could not be validated. Thus a possible explanation for this difference might be due the possible non-specific cross-hybridizations of similar zinc finger proteins when the GeneFilters were used. However, since the known proteins were identified and validated using our study model system, we concluded that our methodology was successful in identifying in identifying transcription factors that were highly differentially expressed during myeloid differentiation such as MAFB. |
