Expression of multiple classes of the nuclear factor-1 family in the developing human brain: differential expression of two classes of NF-1 genes.

Nuclear factor-1 (NF-1) is a multifunctional protein that participates in both transcription and replication. NF-1 proteins exist as a family of proteins that share some common structural and functional features but also demonstrate organ and cell type specific expression. Based upon these characteristics, the family of NF-1 proteins is divided into four classes, A, B, C and D. Several NF-1 binding sites have been identified in the regulatory sequences of the human polyomavirus, JCV, which multiplies most efficiently in glial cells derived from human fetal brain. Nuclear proteins from these cultures bind specifically to these NF-1 sites. It is not known, however, which member(s) of the NF-1 family is expressed in cells susceptible to JCV infection. We have examined glial cells as well as HeLa cells, which are not permissive to JCV, for NF-1 expression. By RT-PCR analysis, all four classes of NF-1 are expressed in human fetal glial cells and HeLa cells. However, by Northern analysis the expression of class D gene is much higher in the glial cells than HeLa cells. Expression of the class C gene, first identified in HeLa cells as NF-1/CTF1, is barely detectable in glial cells but highly expressed in HeLa cells. The screening of cDNA libraries from two early human brain tissues resulted in the identification of a number of clones which appear to be related and belong to a single class of the NF-1 family, class D. Nucleotide sequence of one clone, designated NF-1/AT1, confirms this. The NF-1/AT1 protein was overexpressed in E coli and found to bind specifically to an NF-1 probe by gel shift analysis. Southern analysis of human fetal glial cells indicates that the NF-1/AT1 gene, class D, is derived from a different gene than NF-1/CTF1. These results suggest the possibility that genes or viruses, like JCV, which use NF-1 for their expression in human brain derived cells may preferentially use the NF-1 class D protein.