Transcription in Sciara coprophila polytene chromosomes: DNA and RNA puffs

Leung, Julia Siu-Pen

Full Metadata

Overview

Year:: 2017
Contributor:: Leung, Julia Siu-Pen (creator); Gerbi, Susan (Advisor); Wessel, Gary (Reader); Jogl, Gerwald (Reader); Brown University. Department of Molecular Pharmacology, Physiology and Biotechnology (sponsor)
Genre:: theses
Subject:: sciara coprophila; DNA puffs; Fluorescence microscopy; RNA puffs; RNA transcription; Giant chromosomes
Extent:: 8, 53 p.
DOI: https://doi.org/10.7301/Z0CV4G5N

Files

Description

Abstract:: Innate regulatory mechanisms ensure that an origin of replication activates at most once per cell cycle. An override of this control results in multiple firings of origins leading to an accumulation of DNA. This phenomenon, known as DNA re-replication, results in DNA amplification that is a hallmark of cancer. In order to minimize or prevent DNA amplification, it is important to study the initiating mechanism, but this is not possible in cancer cells. However, the DNA puffs found in the salivary gland chromosomes of the fungus gnat Sciara coprophila are one of the only two known cases where intrachromosomal DNA amplification occurs during normal development. Study of the mechanism for overriding regulatory control of the DNA puff origins could be illuminating for further understanding of the mechanics of origin activation, with potential significance for cancer diagnosis and therapy. One facet of DNA puffs that has yet to be unraveled is the relationship between amplification and transcription. Does transcription open up the chromatin structure to facilitate DNA re-replication or is the converse true? Are all highly transcribed genes amplified? Are all amplified genes highly transcribed? What is the temporal relationship between transcription and amplification? Pulse-chase experiments using 5-ethynyl uridine were completed and visualized through a click reaction with azide-Alexa 594 fluorophore to map RNA transcription in Sciara larvae polytene chromosomes at five different developmental stages that span from pre-amplification to post-puff formation. EU incorporation was primarily observed in interchromomeres, which correspond to euchromatin. DNA and RNA puff loci on the four chromosomes all displayed some level of transcription signal in at least one developmental stage. No clear patterns regarding the timing or amount of transcription could be discerned amongst the loci or developmental stages. Not every instance of intense transcription was located at a DNA or RNA puff locus, suggesting that not all highly transcribed genes are amplified or involved in puffing. Transcription seemed to occur somewhat simultaneously with amplification as EU incorporation was detected at DNA puff loci in pre-amplification larvae as well as after visible cytological puffing.
Notes:: Thesis (Sc. M.)--Brown University, 2017

Content

Access Conditions

Rights: In Copyright
Restrictions on Use: Collection is open for research.

Citation

Leung, Julia Siu-Pen, "Transcription in Sciara coprophila polytene chromosomes: DNA and RNA puffs" (2017). Molecular Pharmacology, Physiology, and Biotechnology Theses and Dissertations. Brown Digital Repository. Brown University Library. https://doi.org/10.7301/Z0CV4G5N

Relations

Collection:

Molecular Pharmacology, Physiology, and Biotechnology Theses and Dissertations

Theses and Dissertations for the Molecular Pharmacology, Physiology, and Biotechnology department.
...