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Sequence of a cDNA encoding the ferritin H-chain from an 11-week-old human fetal brain
M Dhar1, V Chauthaiwale, J G Joshi
1Department of Biochemistry, University of Tennessee, Knoxville 37996-0840.
Insights
Human fetal brain ferritin mRNA contains a unique 279 bp sequence in its 3' untranslated region (UTR). This finding suggests differential polyadenylation site selection during ferritin mRNA production in fetal brain versus liver.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Ferritin is crucial for iron storage and homeostasis.
- Human ferritin heavy chain (FTH) gene expression is regulated at multiple levels.
- Understanding tissue-specific mRNA variations is key to comprehending gene regulation.
Purpose of the Study:
- To identify and characterize ferritin transcripts in human fetal brain.
- To investigate sequence differences in ferritin mRNA between fetal brain and liver.
- To elucidate the functional significance of novel sequences in ferritin mRNA.
Main Methods:
- Screening of a human fetal brain cDNA library using a human liver ferritin cDNA probe.
- DNA sequencing of positive clones.
- Northern blot analysis of polyadenylated RNA from human fetal brain.
- Bioinformatic comparison with genomic databases (GenBank, EMBL).
Main Results:
- A novel clone, cFB1, from fetal brain showed high similarity to liver ferritin cDNA in coding and 5'/3' untranslated regions (UTR).
- A unique 279 bp sequence was identified within the 3'-UTR of the fetal brain ferritin transcript.
- This 279 bp sequence showed partial homology to non-transcribed regions of FTH genomic sequences in human, mouse, and rat.
- Northern blot confirmed the 279 bp sequence is part of the mature fetal brain FTH mRNA transcript.
Conclusions:
- The 279 bp sequence represents a novel addition to the mature human fetal brain ferritin mRNA.
- This finding indicates differential polyadenylation site selection in the production of FTH mRNA between fetal brain and liver.
- The presence of this unique sequence may have implications for post-transcriptional regulation of ferritin in the developing brain.
Abstract:
A cDNA library in lambda Charon BS(-) from 11-week-old human fetal brain (FB) was screened using a human liver ferritin (FTH)-encoding cDNA as a probe. The complete sequence of the positive clone, cFB1, showed that the coding region and a part of the 5' and 3' untranslated regions (UTR) are identical to the corresponding published sequence of the liver cDNA. However, a particularly noteworthy difference is the presence of 279 bp of additional sequence in the FB 3'-UTR. Northern blot analysis of FB poly(A)+RNA showed it to be a part of the FTH transcript. Comparison of the 279-bp sequence with the GenBank and EMBL databases showed it to be 94.1, 62.5, and 58.9% similar to segments from human, mouse and rat FTH genomic sequences, respectively. However, in all these cases, only a part of this 279-bp sequence has been found in the nontranscribed region. We therefore conclude that in FB, the 279-bp sequence is a part of the mature FTH mRNA. Sequence analysis also suggests a differential poly(A) site selection in the production of FTH mRNA in FB and liver.