We have identified a novel basic leucine zipper (bZIP) protein, designated ATF-7, that physically interacts with the PRL-1 protein-tyrosine phosphatase (PTPase). PRL-1 is a predominantly nuclear, farnesylated PTPase that has been linked to the control of cellular growth and differentiation. This interaction was initially found using the yeast two-hybrid system. ATF-7 is most closely related to members of the ATF/CREB family of bZIP proteins, with highest homology to ATF-4. ATF-7 homodimers can bind specifically to CRE elements. ATF-7 is expressed in a number of different tissues and is expressed in association with differentiation in the Caco-2 cell model of intestinal differentiation. We have confirmed the PRL-1⅐ATF-7 interaction and mapped the regions of ATF-7 and PRL-1 important for interaction to ATF-7's bZIP region and PRL-1's phosphatase domain. Finally, we have determined that PRL-1 is able to dephosphorylate ATF-7 in vitro. Further insight into ATF-7's precise cellular roles, transcriptional function, and downstream targets are likely be of importance in understanding the mechanisms underlying the complex processes of maintenance, differentiation, and turnover of epithelial tissues.

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Mechanisms by which aniline produces selective toxicity to the spleen are not well understood. Previously, studies showed that aniline exposure induces lipid peroxidation and protein oxidation in the spleen. The present study was aimed to determine the release of free iron and oxidative DNA damage in the spleen following aniline exposure. To achieve this, male SD rats were orally administered 1 mmol/kg/d aniline for 7 d, while controls received the vehicle only. Total splenic iron content showed a significant increase of 200% in the aniline-treated rats, whereas free iron (low-molecular-weight chelatable iron) showed a marked increase of 375% in comparison to controls. Oxidative DNA damage, measured in terms of 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels, showed a remarkable increase of 83% in the aniline-treated rats. These results suggest an association between release of free iron and oxidative DNA damage, which could lead to mutagenic and/or carcinogenic responses in the spleen.

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