• Molecules and Cells
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• 제37권12호
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• pp.841-850
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• 2014

Polycomb group (PcG) proteins are conserved chromatin regulators involved in the control of key developmental programs in eukaryotes. They collectively provide the transcriptional memory unique to each cell identity by maintaining transcriptional states of developmental genes. PcG proteins form multi-protein complexes, known as Polycomb repressive complex 1 (PRC1) and Polycomb repressive complex 2 (PRC2). PRC1 and PRC2 contribute to the stable gene silencing in part through catalyzing covalent histone modifications. Components of PRC1 and PRC2 are well conserved from plants to animals. PcG-mediated gene silencing has been extensively investigated in efforts to understand molecular mechanisms underlying developmental programs in eukaryotes. Here, we describe our current knowledge on PcG-mediated gene repression which dictates developmental programs by dynamic layers of regulatory activities, with an emphasis given to the model plant Arabidopsis thaliana.

• Applied Microscopy
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• 제25권4호
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• pp.17-25
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• 1995

This paper aims to probe the cell differentiation and gene activity in early Oogenesis from Dendrolimus spectabilis Butler by transmission electron microscope. The 8 cystocytes are formed by mitosis of the Oogonia, and differentiated to the 1 Oocyte and 7 nurse cells. The oocyte and nurse cells are connected by ring canals, through which the cytoplasmic organelles such as mitochondria, free ribosomes, and electron dense granular materials are passed from nurse cells to o cyte. Many replication fork in the cystocyte nuclei and 2 transcriptional units of $2.7{\mu}m\;and\;0.36{\mu}m\;or\;0.5{\mu}m$ in the nurse cells are observed by the chromatin spreading technique. It is possible that transcriptional units are passed from nurse cells to Oocyte.

• 생명과학회지
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• 제17권4호
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• pp.593-598
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• 2007

Amino acids of histone tail are covalently modified in eukaryotic cells. Lysine residues in histone H3 and H4 are methylated at three levels; mono-, di- or trimethylation. Methylation in histones is related with transcription of the genes in distinct pattern depending on lysine residues and methylated levels. Relation between transcription and methylation has been relatively well understood at three lysines H3K4, H3K9 and H3K36. H3K4 is methylated in active or potentially active chromatin and its methylation associates with active transcription. H3K9 is generally methylated in heterochromatin or repressed gene, but trimethylation of this lysine occur in actively transcribed genes also. Methylation at H3K36 generally correlates with active chromatin/transcription, but the correlation of its dimethylation with transcription is controversial. All together methylation patterns of individual lysine residues in histone relate with activation or repression of transcription and may provide distinctive roles in transcriptional regulation of the eukaryotic genes.

• 대한세포병리학회지
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• 제5권2호
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• pp.99-105
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• 1994

We studied cervical cytology of 175 cases of histologically confirmed microinvasive squamous cell carcinoma of the uterine cervix in Cheil General Hospital from 1991 to 1993. Excluding 32 cases of insufficient smear, 143 cases were reviewed in view of background, cellularity, smear pattern, nuclear chromatin and presence of nucleoli. The characteristic findings of microinvasive carcinoma were syncytia and/or individual tumor cells in the focally necrotic inflammatory background. Nuclear chromatin was clear or fine. Nucleoli were observed in 55%. The prediction rate of microinvasive carcinoma was 74%. There is no significant relationship between the cellular features and depth of invasion.

• Mycobiology
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• 제41권1호
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• pp.1-12
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• 2013

Msi1-like (MSIL) proteins, which are eukaryote-specific and contain a series of WD40 repeats, have pleiotropic roles in chromatin assembly, DNA damage repair, and regulation of nutrient/stress-sensing signaling pathways. In the fungal kingdom, the functions of MSIL proteins have been studied most intensively in the budding yeast model Saccharomyces cerevisiae, an ascomycete. Yet their functions are largely unknown in other fungi. Recently, an MSIL protein, Msl1, was discovered and functionally characterized in the pathogenic yeast Cryptococcus neoformans, a basidiomycete. Interestingly, MSIL proteins appear to have redundant and unique roles in both fungi, suggesting that MSIL proteins may have evolutionarily divergent roles in different parts of the fungal kingdom. In this review, we will describe the current findings regarding the role of MSIL proteins in fungi and discuss future directions for research on this topic.

• 대한세포병리학회지
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• 제19권1호
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• pp.9-15
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• 2008

The major categories of neuroendocrine tumors of lung are typical carcinoid, atypical carcinoid, large cell neuroendocrine carcinoma, and small cell carcinoma. The histologic classification criteria of neuroendocrine tumors are well documented in the "WHO Classification of Tumors" based on mitotic figures and necrosis. Cytologic characteristics of neuroendocrine tumors are trabecular, acinar, and solid arrangement of tumor cells and occasional rosette formation. Nuclear chromatin patterns are characteristically described as "salt and pepper chromatin pattern". Many of cytologic classifications documented in the literature are before the "WHO Classification". In this review, the cytologic features of pulmonary neuroendocrine tumors are documented according to the WHO classification, and recent concepts of neuroendocrine tumors of lung are discussed.

• Animal cells and systems
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• 제16권3호
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• pp.183-189
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• 2012

It has been suggested that chromatin is organized into the stable structures that provide fundamental units of chromosome architecture in interphase mammalian cells. The stable structures of chromatin can be visualized as replication foci when replicating DNA is labeled with thymidine analogs. Previously, we showed that the chromosome territory expanded after BAF53 knockdown. In this study, we found that BAF53 is required for the formation of replication foci. DNA replication was not impaired in BAF53 knockdown cells, suggesting that the decrease in the number of replication foci is due to disintegration of replication foci, but not suppression of DNA replication. The attractive forces that maintain structural integrity of replication foci could be disrupted by BAF53 knockdown, and it may be responsible, at least in part, for the expansion of chromosome territories after BAF53 knockdown.

• 대한의생명과학회지
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• 제29권3호
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• pp.103-108
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• 2023

Enhancers are cis-elements to regulate transcription of cell/tissue-specific genes in multicellular organisms. These elements locate in upstream or downstream regions of target genes and are found in a long distance up to 100 Kb in some cases. Transcription factors and coactivators bind to enhancers in a chromatin environment. Enhancers appear to facilitate the transcription of target genes by communicating with promoters and activating them. As transcription activation mechanism of enhancers, chromatin looping between enhancers and promoters, tracking of enhancer activity to promoters along the intervening regions, and movement of enhancers and promoters into transcription condensates have been suggested based on various molecular and cellular biology studies. These mechanisms are likely to act together rather than exclusive each other for gene transcription. Understanding of enhancer action mechanism may provide a way to regulate the transcription of cell/tissue-specific genes relating with aging or various diseases.

• 한국동물학회:학술대회논문집
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• 한국동물학회 1995년도 한국생물과학협회 학술발표대회
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• pp.326.2-326
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• 1995

No Abstract, See Full Text

• 대한생식의학회:학술대회논문집
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• 대한불임학회 2001년도 제40차 춘계학술대회
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• pp.59-60
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• 2001