Control of Expression Level in Human Genes: Observations with Apoptosis Genes and Genes Involved in B cell Development
Author(s): Jay C. Brown
To understand the way a gene functions in development, one needs to know about the gene product’s functional capabilities, the tissues where it is located, and the level of its expression. It is now widely accepted that transcription factors can affect the level of gene expression, but the results emphasize the need for further clarification. The study described here was carried out to determine whether the amount of a transcription factor bound in the promoter region might be directly related to the level of the gene’s expression. The study was focused on a population of human genes involved in apoptosis, a pathway known to be affected by the transcription factor Ikaros (IKZF1 gene). For each apoptosis gene, information was accumulated about its expression level and about the level of IKZF1 binding in the promoter. The two measurements were then compared and interpreted to identify instances where the amount of IKZF1 binding is related to the level of gene expression. A similar analysis was carried out with genes involved in B cell development, also a gene population influenced by IKZF1. The results identified gene groups, each containing 3-8 genes, in which the expression level was related to IKZF1 binding in the promoter, a result that supports the idea that promoter bound IKZF1 can affect the level of gene expression. A further study was performed to examine the secondary, non-IKZF1 transcription factors bound in the promoters of apoptosis and B cell development genes. Prominent amounts of RBFOX2, ASH2L and TAF1 were observed in both populations suggesting IKZF1-rich promoters may resemble each other in their content of other transcription factor binding sites as well.