Separation and reattachment of a turbulent boundary layer are crucial issues in aeronautical and engineering applications since they are associated with upper bound of efficiency for the devices. Understanding of the underlying physics and the accurate prediction however may not be still sufficient especially for pressure-induced separated flows. In the present work, we have performed a series of direct numerical simulations (DNSs) for a pressure-induced turbulent separation bubble on a flat plate. Suction and blowing are imposed at the upper boundary for producing a separation bubble. The inlet Reynolds number Re_theta based on the freestream velocity and the momentum thickness is equal to 300, 600 and 900, the latter value being three times larger than that of the seminal DNS works (Spalart and Coleman 1997; Na and Moin 1998). In this talk, we first describe effects of varying suction and blowing (i.e. pressure gradients) and compare with the earlier DNS works. We then discuss the Reynolds-number dependence in a large separation bubble. Also discussed are possible scaling laws of the root-mean-square value of wall-pressure fluctuations established on the basis of the relationship with local maximum Reynolds stresses. Finally, the extended DNS work for Re_theta=1500 will be introduced briefly.