Structure and function of the iron-responsive element from human ferritin L chain mRNA

Area of Science:

• Molecular Biology
• Gene Regulation
• Iron Metabolism

Background:

• Ferritin regulates intracellular iron levels.
• Iron-responsive elements (IREs) control ferritin mRNA translation.
• Human ferritin exists in heavy (H) and light (L) subunits.

Purpose of the Study:

• To clone and functionally characterize the IRE of human ferritin L chain mRNA.
• To compare the L-chain IRE structure and function to the H-chain IRE.
• To investigate the role of the L-chain IRE in iron regulation in T lymphocytes.

Main Methods:

• Cloning of the human ferritin L chain IRE from a T lymphocyte cDNA library.
• In vitro binding assays with iron regulatory protein (IRP).
• In vivo studies assessing mRNA translation and polysome mobilization under varying iron conditions.

Main Results:

• The cloned L chain IRE exhibited a distinct palindromic cDNA structure compared to genomic predictions.
• The L chain IRE formed a less stable stem-loop than the H chain IRE.
• Despite structural differences, the L chain IRE efficiently bound IRP in vitro, similar to the H chain IRE.
• In vivo, the L chain IRE repressed translation during iron deprivation and allowed transcript mobilization upon iron repletion.

Conclusions:

• The human ferritin L chain mRNA contains a functional IRE that regulates translation.
• The L chain IRE mediates iron-dependent translational control comparable to the H chain IRE.
• These findings contribute to understanding iron homeostasis regulation at the post-transcriptional level.