Transcriptional regulation of the gene encoding apolipoprotein AI in chicken LMH cells

Previous studies indicated that the differential expression of the chicken gene (ApoAI) encoding apolipoprotein AI (ApoAI) in the QMLA-29 and LMH cell lines may be the result of altered cis-elements and/or trans-acting factors. To examine the cis-elements, LMH DNA was used as a template and the 5'-upstream region of ApoAI was PCR amplified. The nucleotide sequence of the LMH ApoAI upstream region was identical to that obtained from young chicken liver DNA. Band shift analyses of the -87 to +90 bp upstream DNA of ApoAI showed differences in the shifting patterns when nuclear proteins from LMH and liver cells were used. Southwestern blots with the same DNA fragment and nuclear proteins from liver and LMH also showed differences. There was one common band of approx. 65 kDa. In addition, LMH had a trans-acting factor of approx. 26 kDa, while liver had an approx. 46-kDa protein. These data suggest that LMH has a different trans-acting factor which may downregulate ApoAI expression.