1Heat oven to 400°. Dissolve yeast in warm water; set aside.
2Mix flour, sugar, baking powder, baking soda and salt in large bowl. Cut in shortening, using pastry blender or crisscrossing 2 knives, until mixture looks like fine crumbs. Stir in yeast mixture and just enough buttermilk so dough leaves side of bowl and forms a ball.
3Place dough on generously floured surface; gently roll in flour to coat. Knead lightly 25 to 30 times, sprinkling with flour if dough is too sticky. Roll or pat 1/2 inch thick. Cut with floured 2 1/2-inch biscuit cutter. Place about 1 inch apart on ungreased cookie sheet.
4Bake 12 to 14 minutes or until golden brown. Immediately remove from cookie sheet. Brush with butter. Serve hot.