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Figure 4 | BMC Cell Biology

Figure 4

From: Sirtuin-mediated nuclear differentiation and programmed degradation in Tetrahymena

Figure 4

Thd14 resembles a class 1b sirtuin. a Phylogenetic tree comparing the primary structure of the T. thermophila sirtuins including Thd14 (asterisk) with that of the yeast sirtuins (Sir2 and Hst1-4) and the seven human sirtuins (SIRT1-7) (unweighted-pair group methods using average linkages). The scale (x-axis) represents evolutionary distance as calculated using the Poisson correction method, with the units of number of amino acid substitutions per site. b Amino acid sequence of Thd14 translated from the gene sequence. The predicted zinc finger domain is highlighted in grey and the sirtuin domain is highlighted in black. The motifs of conserved amino acids present within the sirtuin core domain are in boldface type. Underlined letters indicate intraclass-conserved residues, used for sirtuin identification. The asterisk denotes the critical catalytic histidine residue in the 'HG' motif that is strictly conserved in all known sirtuins. Boxed is a sub-motif specific to class 1b sirtuins. c Cells expressing HA-Thd14 were grown in the absence "(-)"or presence "(+)" of 1 μg/mL CdCl2 for 2 hrs to induce expression from the MTT1 promoter. Total cellular proteins were resolved by SDS-PAGE, transferred to nitrocellulose membrane, and subjected to immunoblot analysis using α-HA antiserum. d Amino acid alignment of the UBP-type zinc-finger domain from Thd14 with similar domains from murine and Drosophila HDAC6 (mHDAC6 and dHDAC, respectively). Asterisks mark conserved Cys and His residues; black asterisks denote those in HDAC6 that are essential for ubiquitin binding [24]. Conserved residues are shaded in black (for identical residues) and grey (for chemically similar residues).

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