Department launches seminars for human health improvement


The Center for Advanced Biotechnology and Medicine hosted its annual seminar series with a presentation, “Genome-wide Effects of Polycomb Repression: Control of Pervasive Transcription,” by Vincenzo Pirrotta.

Pirrotta, a distinguished professor in the Department of Molecular Biology and Biochemistry, spoke yesterday about the effect certain polycomb complexes had on gene transcription rates.

Some of the sequences in deoxyribonucleic acid are used to create a single strand version of DNA called ribonucleic acid, said Luca Cartegni, an associate professor in the Department of Chemical Biology.

These sequences, known as the promoter regions, determine the amount of RNA created and when it is created, he said. Polycomb transcription regulates this rate.

DNA is a code with four bases, said Stephen Anderson, an associate professor in the Department of Molecular Biology and Biochemistry. A mutation occurs when one of the bases is changed. 

Pirrotta’s talk focused on chromatin modification, which does not change the genome but can alter its expression, he said. This field is known as epigenetics. 

Polycomb complexes are important due to their effect on the human body, said Pirrotta. Polycomb mutations are associated with various diseases and ailments, including cancer.

These complexes regulate important developmental genes, he said. These genes control cell differentiation, or what type of cell is made, and are relatively recent discoveries.

“At the beginning, people didn’t even know about polycomb complexes and such,” he said. “[These complexes] turned out to be extremely important.”

It is now known that polycomb complexes do not bind themselves to specific genes, he said. Rather, they affect genes through a hit-and-run method, where they influence part of the genome and then move to another area.

Transcription is repressed in passage, he said. 

“[Polycomb complexes] prevent the DNA from becoming accessible to transcription machinery,” he said.

Newer information may lead to a reinterpretation of what effect the complex mutations actually have, Pirrotta said.

The research Pirrotta is working on involves repressing gene transcription through the use of histones, a type of alkaline protein. 

A specific histone, known as H3K27, is bonded to a methyl group. This is a type of hydrocarbon, through a polycomb-group known as Polycomb Repressive Complex two, he said. There are two types of polycomb-groups, with the other designated PRC1. 

The polycomb-groups affect the entire genome instead of targeting a specific set of genes, he said.

“There are specific ways to access or antagonize transcription,” he said. 

This was discovered using cultured cell lines, he said. Some of these cultures were normal, while others held certain mutations derived from mutations found in flies.

Research in this field is becoming increasingly important for the impact it will have on other fields such as medicine, Anderson said.


Nikhilesh De

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