Function of the Active Site Lysine Autoacetylation in Tip60 Catalysis

The 60-kDa HIV-Tat interactive protein (Tip60) is a key member of the MYST family of histone acetyltransferases (HATs) that plays critical roles in multiple cellular processes. We report here that Tip60 undergoes autoacetylation at several lysine residues, including a key lysine residue (i.e. Lys-327) in the active site of the MYST domain. The mutation of K327 to arginine led to loss of both the autoacetylation activity and the cognate HAT activity. Interestingly, deacetylated Tip60 still kept a substantial degree of HAT activity. We also investigated the effect of cysteine 369 and glutamate 403 in Tip60 autoacetylation in order to understand the molecular pathway of the autoacetylation at K327. Together, we conclude that the acetylation of K327 which is located in the active site of Tip60 regulates but is not obligatory for the catalytic activity of Tip60. Since acetylation at this key residue appears to be evolutionarily conserved amongst all MYST proteins, our findings provide an interesting insight into the regulatory mechanism of MYST activities

Cool-season annual pastures with clovers to supplement wintering beef cows nursing calves

<p>Abstract</p> <p>In December of 3 years, 87 beef cows with nursing calves (594 ± 9.8 kg; calving season, September to November) at side were stratified by body condition score, body weight, cow age, and calf gender and divided randomly into 6 groups assigned to 1 of 6 cool-season annual pastures (0.45 ha/cow) that had been interseeded into a dormant common bermudagrass (<it>Cynodon dactylon</it> [L.] Pers.)/bahiagrass (<it>Paspalum notatum</it> Flugge) sod. Pastures contained 1 of the following 3 seeding mixtures (2 pastures/mixture): 1) wheat (<it>Triticum aestivum</it> L.) and ryegrass (<it>Lolium multiflorum</it> Lam., <b>WRG</b>), 2) wheat and ryegrass plus red clover (<it>Trifolium pretense</it> L., <b>WRR</b>), or 3) wheat and ryegrass plus white (<it>Trifolium repens</it> L.) and crimson clovers (<it>Trifolium incarnatum</it> L., <b>WRW</b>). All groups had <it>ad libitum</it> access to grass hay (12% crude protein; 58% total digestible nutrients). The second week in December, cow estrous cycles were synchronized and artificially inseminated. In late December, a bull was placed with each group for 60-d. Data were analyzed with an analysis of variance using a mixed model containing treatment as the fixed effect and year as the random effect. Body weight and condition scores did not differ (<it>P</it> ≥ 0.27) among cows between February and June. Calf birth weights or average daily gain did not differ (<it>P</it> ≥ 0.17) among treatments; however, calves grazing pastures with clovers did tend (<it>P</it> = 0.06) to weigh more than calves grazing grass only. Weaning weight per cow exposed to a bull was greater (<it>P</it> = 0.02) for WRR and WRW than WRG. Cows grazing winter-annual pastures containing clovers tended to wean more calf body weight per cow exposed to a bull than cows grazing the grass only pastures.</p