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Housekeeping genes commanded to commit suicide in CpG-cleavage commitment upstream of Bcl-2 inhibition in

L Qi1, K H Sit

  • 1Department of Anatomy, Faculty of Medicine, National University of Singapore, Kent Ridge, 117597, Singapore.

Molecular Cell Biology Research Communications : MCBRC
|August 31, 2000
PubMed

Insights

Epigenetic modulation impacts cell death pathways. Key metabolic and structural genes are commonly regulated in both caspase-dependent and -independent cell deaths, suggesting gene-commanded cell suicide.

Area of Science:

  • Molecular Biology
  • Epigenetics
  • Cell Biology

Background:

  • Cell death pathways, including caspase-dependent and -independent routes, are crucial biological processes.
  • Epigenetic modulation, particularly through CpG islands in gene promoter regions, plays a significant role in regulating gene activity.
  • Understanding common regulatory mechanisms in different cell death pathways is vital for comprehending cellular fate.

Purpose of the Study:

  • To investigate the epigenetic regulation of housekeeping genes common to both caspase-dependent and -independent cell death pathways.
  • To identify specific genes involved in intermediary metabolism and cell structure that are significantly regulated during these cell death processes.
  • To elucidate the role of Bcl-2 in relation to CpG-specific DNA cleavage and other apoptotic markers.

Main Methods:

  • Utilized a focused microarray (genechip) targeting 22 housekeeping genes with canonical CpG islands.
  • Analyzed gene activity changes (at least twofold) common to both FasL-mediated (caspase-dependent) and etoposide-mediated (caspase-independent) cell death.
  • Assessed the effect of Bcl-2 overexpression on CpG-specific DNA cleavage and low-molecular-weight DNA fragmentation.

Main Results:

  • Seven genes involved in energy production (glycolysis, tricarboxylic acid cycle, electron transport chain) were commonly downregulated, indicating energy depletion.
  • Downregulation of pyruvate dehydrogenase E1 gene suggested metabolic acidification, a lethal cellular event.
  • Common downregulation of histone H2A.X and upregulation of alpha-tubulin indicated derangement of cell structure and microtubular dynamics.
  • Bcl-2 overexpression did not prevent megabase DNA cleavage but abolished 200-bp ladder cleavages, suggesting its inhibitory action is downstream of CpG cleavage commitment.

Conclusions:

  • Epigenetic modulation of specific genes is critical and common to both caspase-dependent and -independent cell death.
  • Significant downregulation of energy metabolism and structural genes points towards gene-commanded cell suicide.
  • Bcl-2 acts downstream of the initial CpG-cleavage commitment point in these cell death pathways.

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