DNA sequences required for the expression of the human presenilin 1 (PS1) gene have been identified between - 118 and + 178 flanking the major initiation site (+ 1) mapped in SK-N-SH cells. Several Ets sites are located both upstream as well as downstream from the + 1 site, including an Ets motif present at - 10 that controls 90% of transcription in SK-N-SH cells. However, in SH-SY5Y cells, transcription initiates further downstream and requires an alternative set of promoter elements including a + 90 Ets motif. Ets2, ER81, ERM and Elk1 were identified by yeast one-hybrid selection in a human brain cDNA library using the - 10 Ets motif as a bait. We have shown that ERM recognizes specifically Ets motifs on the PS1 promoter located at - 10 as well as downstream at + 90, + 129 and + 165 and activates PS1 transcription with promoter fragments whether or not they contain the - 10 Ets site. We have now searched for ERM interacting proteins by yeast two-hybrid selection in a human brain cDNA library using the C-terminal 415 amino acid of ERM as a bait. One of the interacting proteins was ZNF237, a member of the MYM gene family. It is widely expressed in different tissues in eukaryotes under several forms derived by alternative splicing, including a large 382 amino acid form containing a single MYM domain, and 2 shorter forms of 208 and 213 amino acids respectively that do not. We show that both the 382 as well as the 208 amino acid forms are expressed in SK-N-SH cells but not in SH-SY5Y cells. Both forms interact with ERM and repress the transcription of PS1 in SH-SY5Y cells. The effect of both C-terminal and N-terminal deletions indicates that the N-terminal 120 amino acid region is required for interaction with ERM in yeast, and furthermore single amino acid mutations show that residues 112 and 114 play an important role. The repression of transcription in SH-SY5Y cells also appears to require the N-terminal potion of ZNF237 and was affected by mutation of the amino acid 112. Data from electrophoretic mobility shift assays indicate that ERM and possibly ZNF237 interact with a fragment of the PS1 promoter.
- Presenilin 1