Journal of Microbiology

Alteration of chromosomal structure within β-Tubulin and flagellar calmodulin genes during differentiation of Naegleria gruberi Amebae into Flagellates: Bok, Jin Woong , Lee, Joo Hun; J. Microbiol. 1995;33(3):222-227.

Abstract: We have examined DNase I sensitivity of β-tubulin and flagellar calmodulin genes which are transiently and coordinately activated differentiation of Naegleria gruberi amebae into flagellates. The DNase I sensitivity of β-tubulin and flagellar calmodulin genes changed in parallel with the changes in transcriptional activity of the respective genes during differentiation. The two genes were resistant to DNase I inamebae stage when transcription of the two genes was inactive. Forty minutes after initiation of differentiation, when the two genes were most actively being transcribed, the two genes showed the highest sensitsivity to DNase I. One hundred and twenty minutes after initiation, the differentiation was completed and transcriptional activity of the two genes decreased to a low level. At this stage, the two genes were resistant to DNase I treatment like the ones at the ameba stage. This change in the DNase I sensitivity of the two genes was not observed when transcription of the two genes was blocked by adding cycloheximide at the beginning of differentiation.

Cloning and sequence determination of α-tubulin, β-tubline and Flagellar Calmodulin cDNAs of Naegleria gruberi: Choi, Youn Jeong , Park, Hye Lee , Lee, Joo Hun; J. Microbiol. 1995;33(1):40-45.

Abstract: Five cDNAs encoding two α-tubulins(α13 and α15), two β-tubulins(β5 and β5), and one flagellar calmodulin (Cal-1) were cloned from naegleria gruberi NB-1 and their nt sequences were determined. The α13(EMBL number X81049) and β1(EMBL number X81050) contained a complete open reading frame for α-tubulin and β-tubulin, respectively. The other three clones (α15, β5 and Cal-1) had a part of coding region and a 3’ untranslated region of the respective genes. The α13, β1 and Cal-1 had no homologous sequences in the coding regions and in the 3’ untranslated sequences. However, the α13 and β1 shared an eight nucleotide (AATACAAA) sequence in front of the respective initiation codons. The AATACAAA sequence was also found in N. gruberi strain NEG α-tubulin cDNA clone(αpT1) at the same position. Comparison of the α13 to the αpT1 revealed another stretch of identical sequence, which is 30 nts long, in the 5’ untranlated region.

Effect of Polyamines on Cellular Differintiation of N. gruberi: Inhibition of Translation of Tubulin mRNA: Yoo, Jin Uk , Kwon, Kyung Soon , Cho, Hyun Il , Kim, Dae Myung , Chung, In Kwon , Kim, Young Min , Lee, Tae HO , Lee, Joo Hun; J. Microbiol. 1997;35(4):315-322.

Abstract: The effects of a polyamine, spermine, on the differentiation of Naegleria gruberi amebas into flagellates were tested. Addition of spermine at early stages of differentiation (until 40 min after the initiation of differentiation) completely inhibited the differentiation. To understand the inhibition mechanism, we examined the effect of spermine treatment on the transcription and translation of differentiation-specific genes during differentiation. Addition of spermine at early stages did not inhibit the accumulation of two differentiation-specific mRNAs, α-tubulin and Class I mRNA, significantly, but rather prevented the rapid degradation of the mRNAs in later overall protein synthesis partially and gradually. However, translation of the α-tubulin mRNA was completely inhibited. These data suggest that the inhibition of differentiation of N. gruberi by spermine treatment did not result from the inhibition of transcription of differentiation-specific genes but from the specific inhibition of translation of the mRNAs during the differentiation.

Regulation of Actin Gene Expression During the Differentiation of Naegleria gruberi: Misook Kim , JooHun Lee; J. Microbiol. 2001;39(1):42-48.

Abstract: The regulation of actin gene expression during the differentiation of Naegleria gruberi was examined. Actin mRNA concentration was maximal in amoebae and decreased rapidly after the initiation of differentiation. At 20 min after initiation, the concentration of actin mRNA decreased to 55% of the maximal value. The actin mRNA concentration decreased to the minimum at 80 min (15% of the maximum), and then began to increase slightly at the end of differentiation. This decrease of actin mRNA concentration was regulated by the repression of actin gene transcription based on nuclear runon transcription experiments. The rates of transcription of actin gene in nuclei prepared at 40 and 80 min after the initiation of differentiation were 50 and 28% of that of nuclei prepared at the beginning of differentiation, respectively. The addition of cycloheximide at the initiation of differentiation inhibited both the rapid decrease in the concentration of actin mRNA and the repression of actin gene transcription. These results suggest that the rapid decrease in the concentration of actin mRNA during the differentiation of N. gruberi is accomplished by the repression of actin gene transcription and this transcriptional regulation requires continuous protein synthesis during the differentiation.

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