Project: Research project

Project Details


The long term objective is to understand the molecular mechanisms
involved in the regulation of human surfactant protein A (SP-A) gene
expression. Towards this goal and based on current available information
we propose a number of studies. Current knowledge suggests that there
are two functional SP-A genes. cDNA sequences are available for both
genes but genomic DNA sequence is available for only one. In this
proposal we will first characterize the human SP-A locus, determine the
number of genes, study their chromosomal organization, and determine
their DNA sequence similarities/differences in order to assess potential
similarities/differences in their regulation. Regulation of SP-A gene
expression appears complex and unusual in certain regards. Knowledge
obtained from the first aim will help design experiments to distinguish
whether all SP-A genes are regulated similarly or whether the observed
complexity is due to the fact that different SP-A genes respond
differently to a given signal. Experiments in aims 2-4 comprise two
groups. Since our preliminary data suggest differential regulation by
glucocorticoids of SP-A genes in explant culture, in the first group of
experiments (aim 2) we will study the basic mechanisms that underlie
differential regulation of the SP-A genes in explants, by examining their
expression in the absence of serum and hormones and by further
characterizing the response to glucocorticoids. In the second group of
experiments we will study molecular mechanisms that may be involved in
tissue-specific and developmental stage-specific expression of SP-A genes
(aim 3) as well as hormone-responsive factors that may be important for
differential regulation of SP-A mRNA stability (aim 4). For this group
of experiments emphasis will be placed on trans-acting factors for two
major reasons. Firstly SP-A expression is tissue-specific. In
preliminary experiments aimed at studying tissue-specific expression as a
means of addressing SP-A gene regulation, we identified cis-acting
elements that form tissue-specific and developmentally-specific
DNA/protein complexes. Experiments are designed to further characterize
these factors and assess their functional role in this process.
Secondly, one of the mechanisms involved in the regulation of SP-A
expression in response to glucocorticoids is mRNA stability and inhibitor
studies suggest that a trans-acting factor is also involved in this
process. Preliminary studies show differences in 3'untranslated region
(3'UT) of the SP-A genes/alleles, including the presence or absence of an
11bp segment. Since elements in the 3'UT are often involved in
mechanisms of mRNA stability we hypothesize that this 11bp segment
provides or disrupts a binding site for a regulatory factor. Experiments
in aim 4 will test this hypothesis. Information obtained from the
proposed studies will provide a better definition of the SP-A locus and
shed light on the molecular mechanisms of differential and
tissue-specific regulation. Knowledge gained can be used to study
molecular alterations in the regulation of SP-A gene expression in the
disease state.
Effective start/end date1/1/9312/31/93


  • National Heart, Lung, and Blood Institute

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