Structures of human genes coding for cytokine LD78 and their expression

Area of Science:

• Immunology and Molecular Biology
• Gene Expression and Regulation

Background:

• LD78 belongs to a novel superfamily of small inducible proteins implicated in inflammatory responses, wound healing, and tumorigenesis.
• Understanding the genetic basis and regulation of LD78 is crucial for its role in biological processes.

Purpose of the Study:

• To characterize the genomic structure of LD78 and investigate its gene expression patterns in human cells.
• To determine the transcriptional regulation of LD78 genes in response to specific stimuli.

Main Methods:

• Southern blot analysis was used to identify and map LD78 genomic DNA fragments.
• Human myeloid cell lines (HL-60, U937), a glioma cell line (U105MG), and primary fibroblasts were treated with phorbol 12-myristate 13-acetate (PMA) and cycloheximide.
• RNA hybridization and mRNA phenotyping were employed to assess gene transcription.

Main Results:

• Two homologous LD78 genes, LD78 alpha and LD78 beta, were identified, with varying copy numbers in the human genome.
• PMA treatment rapidly increased LD78-hybridizable RNA levels in HL-60, U937, U105MG cells, and fibroblasts.
• Cycloheximide differentially affected PMA-induced LD78 RNA expression across cell types, indicating complex regulatory mechanisms.
• Both LD78 alpha and LD78 beta genes were found to be transcribed in PMA-stimulated U937 cells.

Conclusions:

• The human genome contains at least two LD78 genes, alpha and beta, with distinct genomic organization and copy numbers.
• LD78 gene expression is inducible by PMA in various human cell types, suggesting a role in cellular responses.
• The regulation of LD78 transcription involves complex pathways sensitive to protein synthesis inhibition, highlighting cell-specific responses.