p38 Mitogen-activated Protein Kinase Mediates the Transcriptional Induction of the Atrial Natriuretic Factor Gene through a Serum Response Element

Abstract

In various cell types certain stresses can stimulate p38 mitogen-activated protein kinase (p38 MAPK), leading to the transcriptional activation of genes that contribute to appropriate compensatory responses. In this report the mechanism of p38-activated transcription was studied in cardiac myocytes where this MAPK is a key regulator of the cell growth and the cardiac-specific gene induction that occurs in response to potentially stressful stimuli. In the cardiac atrial natriuretic factor (ANF) gene, a promoter-proximal serum response element (SRE), which binds serum response factor (SRF), was shown to be critical for ANF induction in primary cardiac myocytes transfected with the selective p38 MAPK activator, MKK6 (Glu). This ANF SRE does not possess sequences typically required for the binding of the Ets-related ternary complex factors (TCFs), such as Elk-1, indicating that p38-mediated induction through this element may take place independently of such TCFs. Although p38 did not phosphorylate SRF in vitro, it efficiently phosphorylated ATF6, a newly discovered SRF-binding protein that is believed to serve as a coactivator of SRF-inducible transcription at SREs. Expression of an ATF6 antisense RNA blocked p38-mediated ANF induction through the ANF SRE. Moreover, when fused to the Gal4 DNA-binding domain, an N-terminal 273-amino acid fragment of ATF6 was sufficient to support trans-activation of Gal4/luciferase expression in response to p38 but not the other stress kinase, Nterminal Jun kinase (JNK); p38-activating cardiac growth promoters also stimulated ATF6 trans-activation. These results indicate that through ATF6, p38 can augment SRE-mediated transcription independently of Ets-related TCFs, representing a novel mechanism of SRF-dependent transcription by MAP kinases.

Megakaryoblastic Leukemia-1/2, a Transcriptional Co-activator of Serum Response Factor, Is Required for Skeletal Myogenic Differentiation

“…Luciferase reporter plasmids with the promoter sequences of cardiac ␣-actin, SM22, atrial natriuretic factor, c-jun (JC6), and 5ϫGAL4-E1B-luc were as described (41)(42)(43)(44). The human smooth muscle ␣-actin luciferase reporter was a gift of C. Chandra Kumar.…”

Ischemia Activates the ATF6 Branch of the Endoplasmic Reticulum Stress Response

“…Accordingly, sub- cellular fractionation and immunoblotting were used to examine the effects of sI and sI/R on ATF6 processing and translocation in cultured cardiac myocytes. There are two forms of ATF6; ATF6␣ and ATF6␤ are both cleaved during ER stress, and the N-terminal fragments translocate to the nucleus, where they bind to ERSEs and influence ER stress response gene expression (28,30,52,53). However, upon activation, ATF6␣ is extremely labile, making it difficult to detect after cleavage and translocation, whereas ATF6␤ is much more stable (23,40).…”

Sarco/endoplasmic Reticulum Calcium ATPase-2 Expression Is Regulated by ATF6 during the Endoplasmic Reticulum Stress Response

“…Recent studies have demonstrated that the N-terminal domain of ATF6 is responsible for transcriptional activation when fused to a heterologous DNA-binding domain (11), whereas the central region of ATF6 possesses a b-Zip domain that is characteristic of some DNA-binding proteins. It has been shown in HeLa cells that full-length ATF6, composed of 670 amino acids, resides in the ER membrane; the region of ATF6 responsible for anchoring it in the ER membrane is located in the approximate center of the protein, between amino acids 378 and 398 ( Fig.…”