A prominent attorney who worked with self-exiled political trial lawyer Shun Chetty was placed under a five-year ban here last night.

The banning of Priscilla Jana, 35, comes just a few weeks after Alwyn Schlebusch, minister of justice and interior, told opposition politician Helen Suzman that he was reviewing banning orders now in force. As of last October, 146 people were banned in South Africa, according to the South African Institute of Race Relations.

Queries today about the reason for Jana's banning went unanswered. This is Schlebusch's first new banning order. On July 31 he reimposed a ban for two years on Nontsikelelo Sisulu, 60, wife of the black nationalist leader Walter Sisulu now serving a life sentence in prison. Mrs. Sisulu has been banned for the past 15 years.

Suzman expressed disappointment at the news of Jana's banning saying, "I was rather hoping the minister would be unbanning people instead of imposing more bannings."

Both Schlebusch's proposed banning review and his statement Aug. 17 that a judicial commission of inquiry soon would be appointed to study the country's tough security legislation were being taken here as signs of a more flexible approach to the treatment of political dissidents by the administration of Prime Minister Pieter W. Botha.

Because she has been banned, Jana cannot be quoted but a close family friend, Josuf Veriava, said it is believed there is no connection between the ban and the sudden flight of Chetty Aug. 8. Chetty left amid a controversy involving allegations of financial and professional misconduct. Jana has not been mentioned in the allegations.

She is, however, a vocal opponent of apartheid and as represented many blacks in security trials. Sources close to the family say the ban was not entirely unexpected.

Jana handled legal affairs for Winnie Mandela, also a banned woman and wife of jailed black nationalist leader Nelson Mandela. Recently, Jana was the attorney in the controversial trial of Solomon Mahlangu, hanged last April for his part in the 1977 slaying of three whites. Mahlangu was regarded as a "freedom fighter" by blacks but as a "terrorist" by whites.

Banning is an arbitrary restriction imposed by the government on persons whose political views and activities are regarded as threatening, many times because the persons are sources of inspiration to others who oppose apartheid. Since bannings became a regular practice in the early 1950s, nearly 1,500 people have been banned. No court hearing is held before the ban is imposed, and the victim is never given a reason for the ban.

Jana's banning order provides that she cannot be in the company of more than one person at a time except in the course of her work as an attorney. She cannot go outside the township of Lenasia where she lives except to Johannesburg.

The order permits her to continue working as an attorney, but the restrictions will make that very difficult. In addition, as a banned person she cannot communicate with other banned people, which rules out many of her clients, such as Mandela.