Caspase 3/caspase-activated DNase promote cell differentiation by inducing DNA strand breaks

Abstract

Caspase 3 is required for the differentiation of a wide variety of cell types, yet it remains unclear how this apoptotic protein could promote such a cell-fate decision. Caspase signals often result in the activation of the specific nuclease caspase-activated DNase (CAD), suggesting that cell differentiation may be dependent on a CADmediated modification in chromatin structure. In this study, we have investigated if caspase 3/CAD plays a role in initiating the DNA strand breaks that are known to occur during the terminal differentiation of skeletal muscle cells. Here, we show that inhibition of caspase 3 or reduction of CAD expression leads to a dramatic loss of strand-break formation and a block in the myogenic program. Caspase-dependent induction of differentiation results in CAD targeting of the p21 promoter, and loss of caspase 3 or CAD leads to a significant down-regulation in p21 expression. These results show that caspase 3/CAD promotes cell differentiation by directly modifying the DNA/nuclear microenvironment, which enhances the expression of critical regulatory genes.development | gene expression | non-apoptotic caspase activity | epigenetics

Regulation of Pax7 protein levels by caspase-3 and proteasome activity in differentiating myoblasts

“…Accordingly, the intensity of the low molecular weight bands increased when the myoblasts were cultured in differentiating conditions (Fig.1A), which correlates with previously described increase in Pax7 degradation upon induction of muscle differentiation [Olguin et al 2007]. Members of the calpains and caspases families of proteases play critical roles in muscle differentiation [Fernando et al 2002;Liang et al 2006;Larsen et al 2010]. Based on the observations described above and in silico analysis of Pax7 sequence indicating potential calpain and caspases cleavage sites (Olguín H., unpublished results), we hypothesized that calpain and/or caspases dependent pathways could be involved in the post-translational regulation of Pax7.…”

“…On the other hand, Pax7 levels were up-regulated in the presence of the caspase inhibitor only in cells cultured in differentiating conditions. Among different caspases isoforms, caspase-3 has been specifi cally involved in the initiation of muscle differentiation and myoblast fusion [Fernando et al 2002;Larsen et al 2010]. Accordingly, we observed a ~2.5-fold increase in Pax7 protein levels upon specifi c caspase-3 inhibition (Fig.…”

A matter of regeneration and repair: caspases as the key molecules

“…The hypothesis that caspase-3 may interact with several factors to initiate the expression of genes that lead to differentiation of specific cell types has been suggested (Abdul-Ghani and Megeney, 2008). A finding that supports this hypothesis is that caspase-3-activated DNase activity leads to cell differentiation by increasing the expression of key regulatory genes (Larsen et al, 2010). Further important support of this hypothesis was put forward by Janzen et al (2008), namely that a decrease in early B lymphocyte development, which is a very late step in the self-renewal process of hematopoietic stem cells, occurs with loss of caspase-3.…”

Chromatin Collapse during Caspase-dependent Apoptotic Cell Death Requires DNA Fragmentation Factor, 40-kDa Subunit-/Caspase-activated Deoxyribonuclease-mediated 3′-OH Single-strand DNA Breaks

“…More recently, the SSBs generated during terminal differentiation of skeletal muscle cells have been attributed to DFF40/CAD (54,55). These DNA strand breaks commonly accumulate in specific DNA sequences placed at the nuclear matrix attachment regions (56).…”