Characterization of nuclear factors modulating the apolipoprotein D promoter during growth arrest: Implication of PARP-1, APEX-1 and ERK1/2 catalytic activities

Abstract

Human Apolipoprotein D (apoD) is upregulated under several stress conditions and pathological situations such as neurodegenerative diseases and cancers. We previously showed that apoD mRNA expression is induced in growth-arrested cells and demonstrated the specific binding of nuclear proteins to the region -514 to -475 of the promoter. Such region contains a pair of Serum Responsive Elements (SRE), an Ets-Binding Site (EBS) and a Glucocorticoid Responsive Element (GRE). In this study, we show that Parp-1, HnRNP-U, CBF-A, BUB-3, Kif4, APEX-1 and Ifi204 bind these regulatory elements of the apoD promoter. Specific binding of HnRNP-U and Parp-1 was confirmed by Electrophoretic Mobility Shift Assay (EMSA). In a biotin pull-down assay, Kif4 and BUB-3 bind preferentially the SRE1 and the EBS-GRE sites, respectively, while APEX-1 seems recruited indirectly to these elements. We found that the mRNA expression of some of these binding factors is upregulated in growth-arrested cells and that these proteins also transactivate the apoD promoter. In agreement with these results, mutants of APEX-1 and of Parp-1 defective for their DNA-binding and catalytic activities could not transactivate the promoter. The knockdown of Parp-1 and HnRNP-U and the use of specific inhibitors of MEK1/2 and of Parp-1 also inhibited the induction of apoD gene expression. Moreover, ERK1/2 was found activated in a biphasic manner post serum-starvation and the inhibition of Parp-1 causes a sustained activation of ERK2 but not ERK1 for up to 2h. Altogether, these findings demonstrate the importance of Parp-1, APEX-1 and ERK1/2 catalytic activities in the growth arrest-induced apoD gene expression.

Chromatin maintenance by a molecular motor protein

“…In line with such a role, a recent study has demonstrated that KIF4 binds to SRE1 (serum responsive)-EBS (ETS binding site)-GRE (glucocorticoid responsive element) of the ApoD promoter under normal growth conditions and that PARP-1 binding to the same promoter under growth arrest condition is modulated by KIF4. 27 Heterochromatin domains are typically late replicating and are maintained by the interplay of structural chromatin proteins, chromatin assembly factors and histone modifiers. [28][29][30] Since heterochromatin decondensation in the absence of KIF4 was only observed in about 30% of unsynchronized cells (Fig.…”

Apolipoprotein D subcellular distribution pattern in neuronal cells during oxidative stress

“…The Apo D promoter contains several potential regulatory elements like serum, acute phase or stress response elements (SRE, APRE, STRE), an alternating purine-pyrimidine stretch implicated in the response to growth arrest, activation proteins 1 and 2 (AP-1, AP-2) and nuclear factor kappa B (NF-kB) binding sites that may be implicated in Apo D responses (Lambert et al, 1993;Levros et al, 2010). Moreover, it has been shown that some Apolipoprotein E (Apo E) isoforms, E3 and E4, can bind and regulate the Apo D promoter activity (Levros et al, 2013).…”

Control of the neuroprotective Lipocalin Apolipoprotein D expression by alternative promoter regions and differentially expressed mRNA 5’ UTR variants

“…The regulation of ApoD gene expression has been studied in detail by analyzing experimentally the promoter region of human ApoD [21,52,53]. A region of~2 kb upstream of human ApoD exon 1 was reported to contain regulatory elements, such as an alternating purinepyrimidine stretch and serum-responsive elements (SRE), that regulate ApoD expression upon a metabolic insult (serum deprivation) [52].…”